Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/ftp/proposer/cycle9/Abstract-Catalog Дата изменения: Wed Jan 5 22:38:55 2000 Дата индексирования: Sat Dec 22 12:53:12 2007 Кодировка: Поисковые слова: reflection nebula

Cycle 9 Abstract Catalog (based on Phase I Submissions)
Generated on: Wednesday January 05, 2000

Proposal Category: GO
Scientific Category: COS
ID: 8559
Title: The Role of Dark Matter in Cluster Formation and Galaxy
Evolution
PI: Richard Ellis
PI Institution: California Institute of Technology

The outer regions of massive clusters represent transitional areas of great
cosmological importance where field galaxies encounter the steep potential
wells of dark matter and baryonic hot gas. Little is known about either the
dark matter profile at large radii or the morphological properties of
infalling galaxies at those redshifts where strong evolution is observed in
the cluster cores. The former is central to understanding the puzzling high
baryonic fraction observed in cluster cores with clear implications for the
mean mass density, Omega_o. Understanding the mass distribution on large
scales will also help separate cosmological field galaxy evolution from that
driven by the environment. To address these questions we propose a wide-field
imaging survey of the rich cluster Cl0024+1654 (z=0.40) which takes advantage
of an extensive galaxy redshift survey we have compiled. We have designed an
efficient sampling strategy which will simultaneously track the gravitational
shear to at least simeq5h_50^-1 Mpc using proven mass reconstruction
techniques developed with ground and HST-based data and connect this dark
matter profile with the radial dependence of star formation, dynamical and
morphological properties of recently-arrived cluster members.
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Proposal Category: GO
Scientific Category: COS
ID: 8560
Title: Large Scale Structure at z ~ 0.9
PI: Lori Lubin
PI Institution: California Institute of Technology

We are requesting deep, broad-band red WFPC2 images of three fields within a
supercluster at z ~ 0.9 in order to study the morphological properties of
galaxies within a high-redshift large scale structure. Because significant
evolution has already been observed in galaxy populations at this redshift,
these observations will provide a crucial link between the global properties
of large scale structure and galaxy-scale physics. The target supercluster
contains two clusters which have already been well-studied by the proposers
with Keck and HST. CL1604+4304 and CL1604+4321 are typical of Abell richness
class 1 to 3 clusters. They are separated by 4100 km s^-1 and by only 7
h_0.7^-1 Mpc. This system is one of only two superclusters that are known at
z ~great 0.9. The proposed HST fields cover the outskirts of the two clusters,
as well as the very central supercluster region. These data will be combined
with previous HST observations of the cluster cores to generate a complete
sample of distant galaxies in a nearly contiguous area corresponding to 1 Mpc
* 10 Mpc. The HST imagery, combined with a Palomar/Keck program to obtain
photometric and spectroscopic coverage of the same region, will allow us to
quantify the morphology--density relation over a wide range of local
environments and to study the relationship between galaxies, clusters, and
their surrounding large scale structure in the high-redshift universe.
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Proposal Category: GO
Scientific Category: COS
ID: 8561
Title: The Ionizing Flux from Star-Forming Galaxies
PI: Matthew Malkan
PI Institution: University of California

Meaningful upper limits on the amount of ionizing radiation from galaxies in
the current epoch have been obtained (by HUT) for only 3 galaxies. The
contribution of normal galaxies to the cosmic UV background flux is even more
uncertain at earlier times. We propose to determine the emission of normal,
intermediate-redshift, star-forming galaxies in the FUV. If their average
escaping ionizing flux is even 1/10 of their strong mid-UV flux, they are a
comparable or even larger source of the background than AGN. Even a small
contribution from the numerous normal galaxies has far-reaching implications
for the strength, spectrum, and spatial homogeneity of the diffuse ionizing
flux. This ionization controls the properties of the young IGM, from the Ly-
alpha forest to protogalaxies. The STIS/FUV-MAMA imager can provide an
extremely sensitive measurement of the pure Lyman-limit continuum from the
brightest galaxies at 1.1 <= z <= 1.7. Our integrations will be deep enough
to provide detections or highly significant (50Sigma) upper limits, for more
than three times as many galaxies as have been previously published (and those
were only at low redshift). If the average ratio of Lyman limit/mid-UV fluxes
is even as small as a few percent, these proposed observations will
underlinedetect it.
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Proposal Category: GO
Scientific Category: COS
ID: 8562
Title: Probing the Large Scale Structure: Cosmic Shear
observations with STIS
PI: Peter Schneider
PI Institution: Max-Planck-Institut f. Astrophysik

The distortion of light bundles from distant galaxies probes the statistical
properties of the intervening inhomogeneous (dark) matter distribution. Its
tidal gravitational field distorts the observable image shapes thereby causing
a coherent ellipticity pattern (Cosmic Shear). The statistical properties of
this pattern reflect those of the large-scale matter distribution in the
Universe. Cosmic Shear can therefore probe the LSS without any reference to
the relation between dark and luminous matter. Owing to the small magnitude
of this effect, a reliable measurement of Cosmic Shear requires superb imaging
of very faint objects. From our detailed and successful preliminary work on
existing parallel imaging data with STIS, we have demonstrated that STIS
provides the required image quality for this program due to its good pixel
sampling and its small PSF anisotropy. We propose an imaging Parallel Program
for Cycle 9, similar to that carried out in Cycle7. We propose to dedicate
one and two orbit parallel opportunities to imaging with the 50CCD `Clear'
filter. By combining the results from these two programs, we expect to measure
the Cosmic Shear on the STIS angular scale with high precision. Comparison
with light tracing through very large N-body simulations will allow us to
constrain the cosmological parameters and fix the normalization of the dark
matter power spectrum with high accuracy.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8563
Title: Determining the Duplicity of Nearby T Dwarfs (Methane
Brown Dwarfs)
PI: J. Davy Kirkpatrick
PI Institution: Infrared Processing and Analysis Center

Knowing the binary fraction of T-type dwarfs (methane brown dwarfs) is crucial
to accurate determinations of the T-dwarf space density and mass function,
especially since equal-magnitude binaries can introduce significant biases in
photometric distance estimates. Because a recent study of slightly hotter L
dwarfs indicates that 30\ equal-magnitude binaries, we believe that T dwarfs
may show a similar tendency to form equal-mass pairs. Characterization of the
T-dwarf multiplicity fraction is necessary if properties of the first few
discoveries are to be adequately applied to larger samples uncovered later. We
propose to image ten newly discovered T dwarfs using the incomparable
resolution of WFPC2, where colors from the F814W and F1042M filters will
provide discrimination of background sources. This imaging program will not
only be able to split close binaries, but will also be capable of detecting
wider companions up to four magnitudes fainter than the T dwarf primary. This
will enable us to probe to temperatures around 500K, much cooler than any
brown dwarf previously identified and squarely in the regime occupied by
young, high-mass planets.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8564
Title: Measuring the Evolution of the UV Upturn
PI: Thomas M. Brown
PI Institution: Goddard Space Flight Center

We propose far-ultraviolet observations of CL1358+62, a rich, well-studied
cluster of galaxies at z =0.33. These observations will provide the first
completely unambiguous measurement of far-UV emission in quiescent ellipticals
at moderate redshift. Theoretically, the strength of far-UV emission
(relative to flux at longer wavelengths) is the most rapidly evolving feature
in elliptical galaxies. Models suggest that this ``UV upturn'' can change by a
factor of 25 over a few Gyr, and it is expected to fade rapidly with
increasing redshift. Surprisingly, the Faint Object Camera (FOC) found strong
far-UV emission in four elliptical galaxies at z=0.375, suggesting no
evolution in this diagnostic between our own epoch and one 4 Gyr earlier.
However, the FOC measurement was particularly susceptible to systematic
errors, and it was limited to a small number of galaxies in just one cluster.
In contrast to the FOC results, recent Space Telescope Imaging Spectrograph
(STIS) observations at z=0.55 obtained very weak detections of ellipticals at
higher redshift, as expected for ellipticals much younger than those in our
own epoch. Observations with the STIS far-UV camera are not subject to the
uncertainties of the FOC measurements, because the STIS camera is blind to
flux at longer wavelengths. Our observations of CL1358+62 will unambiguously
test the apparent lack of evolution in the UV upturn over the past 4 Gyr.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8565
Title: Where Does Lyman Alpha Escape from Galaxy Disks?
PI: William Keel
PI Institution: University of Alabama

The frequent detection of Lyman Alpha emission at high redshifts underscores
the need to understand how it arises in nearby galaxies. Despite the obstacles
posed by radiative transfer, we find empirically that significant Lyman Alpha
emerges from some nearby galaxies. Data on M33, in particular, suggest that
much of this escape could be from the diffuse ISM rather than from H II
regions specifically, an idea with some theoretical attraction as well. This
proposal examines the structure of known Lyman Alpha emission from the
starburst disk of PG 0119+229, to separate the contributions of discrete and
diffuse sources of this line.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8566
Title: High Resolution UV/X-ray Spectroscopy of SMC X-1
PI: Saeqa Vrtilek
PI Institution: Smithsonian Astrophysical Observatory

We propose simultaneous observations of the X-ray pulsar SMC X-1 and its B0
companion SK160 with HST/STIS, Chandra, and ground-based optical telescopes.
We will search for correlation between orbital phase and ``bleaching'' of
important P Cygni lines by X-ray photoionization (Hatchett-McCray effect). We
will model the simultaneous X-ray, ultraviolet, and optical continuum emission
at different phases of the superorbital period to measure changes in mass
accretion rate, disk structure, and disk size. Using the Time-Tag mode, we
will search in the ultraviolet for aperiodic variability near 0.1-0.2 Hz
throughout the lines and continuum and for the 0.7 second X-ray pulsar period.
Using the Chandra ACIS-S in CC mode we will conduct pulse-phased spectroscopy
of the X-ray emission. Our multiwavelength observations will enable us to
analyze the density structure and composition of the wind; set limits on the
size, shape, rotation, and precession of the disk; and determine the effects
of X-ray illumination on the disk, the star, and the stellar wind.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8567
Title: Confirming the parallax of the neutron star RX J185635-
3754
PI: Frederick Walter
PI Institution: State University of New York

Cycle 6 and 7 observations of the isolated neutron star RX J185635-3754 have
revealed a motion of 0.8 arcsec in 2.5 years. This is a combination of the
annual parallax and the proper motion. A third observation, planned for this
fall, will formally yield sufficient information to solve for the parallax and
proper motion independently. This first ever measurement of the distance of
an isolated neutron star has important ramifications for astrophysics and for
nuclear physics. The magnitude of the expected parallactic shift is less than
one PC pixel, and must be measured against a far larger shift due to the
proper motion. While this parallactic shift is in principle measurable for
distance up to about 100 pc, these real data are subject to subtle
instrumental effects which may skew the results. Given the scientific
importance of obtaining an accurate distance, we request a fourth epoch
observation to confirm the parallax.
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8568
Title: A Seminal Spectroscopic and Imagery Investigation of the
Brightest Wolf-Rayet Shell Nebula: NGC 6888
PI: Reginald Dufour
PI Institution: Rice University

We propose to obtain HST WFPC2 imagery and STIS UV-optical-NIR spectroscopy of
several regions in the brightest Wolf-Rayet Shell Nebula (WRSN), NGC 6888. The
physical conditions in the wind-driven and/or stellar ejected plasma
(temperature, density, ionization, and composition) of WRSN, which are
dominated by strong stellar winds from hot massive stars in an advanced state
of evolution, often involve emission from both shock-ionized and photoionized
gas in close proximity. These new observations will comprise the first
combined spectroscopy and imagery of a WRSN at a resolution sufficient (i.e.,
~ 10^15 cm) to separate and individually analyze these two emission regions.
We also expect to obtain the first determination of the abundance of carbon -
a key element in the He-C-N nucleosynthesis chain - in WRSN, of which several
are known to be nitrogen- and helium-enriched by mass loss during its previous
red supergiant phase. These observations will also be used to evaluate the
contribution of stellar wind-driven shock emission as a source of temperature
fluctuations, important for accurate abundance determinations within this and
other types of nebulae, such as planetary nebulae and H ii regions.
================================================================================
Proposal Category: GO
Scientific Category: QAL
ID: 8569
Title: A New Survey for Low-Redshift Damped Lyman-Alpha Lines in
QSO MgII Systems
PI: Sandhya Rao
PI Institution: University of Pittsburgh

-0.15 truein Studies have shown that most of the observable neutral gas mass
in the Universe resides in QSO damped LyAlpha (DLA) systems. However, at low
redshift (z<1.65), DLA can only be found by searching in the UV with HST.
Such searches are crucial since z<1.65 corresponds to ~ 3/4 of the age of the
Universe. The identification of significant numbers of low-redshift DLA
systems is imperative if we ever hope to effectively study this cosmologically
massive component of neutral gas. To this end, we recently reported on the
results of our initial HST survey to study low-redshift DLA absorbers in QSO
MgII systems. We discovered 14 DLA systems and had a success rate of ~14\
these results and our improved understanding of the selection criteria for
successful DLA searches, we propose a new survey for low-redshift DLA lines in
QSO MgII systems. With our new revised selection criteria, we can empirically
show that our success rate would be ~35\ Specifically, we propose to observe
the LyAlpha line of 71 MgII systems. We estimate that we will discover ~25
new DLA systems with redshift z<1.65. Finding these systems will facilitate
the type of research that can be done with DLA systems. By boot-strapping from
the MgII statistics, we will be able to further improve the determination of
the low-redshift statistical properties of DLA (their incidence and
cosmological mass density) and open up new opportunities for studies at low
redshift.
================================================================================
Proposal Category: GO
Scientific Category: QAL
ID: 8570
Title: HS 1543+5921: A bright quasar seen through a nearby star-
forming dwarf galaxy
PI: Regina Schulte-Ladbeck
PI Institution: University of Pittsburgh

-0.15truein Recently, the nearby star-forming dwarf galaxy SBS 1543+593
(z=0.009) was discovered to be superimposed upon the bright quasar HS
1543+5921 (z~0.8, m_B=16.8). Very few such alignments are known, making HS
1543+5921/SBS 1543+593 a unique system for absorption-line studies with HST.
In order to investigate the properties of SBS 1543+593 and determine the
utility of future work, we request 2 orbits for a small pilot project. First,
we propose to obtain a STIS spectrum which will allow us to determine the HI
column density in the sight-line through the dwarf. Second, we propose to
obtain a near-UV image of SBS 1543+593 with WFPC2 (to be used with ground-
based images). The image will allow us to ascertain the dwarf galaxy's
morphological type (spiral or irregular), details of its star formation, and
investigate whether amplification bias due to the gravitational lens effect
plays a role in the appearance of this improbable alignment. An exciting
discovery which might result from this study is that SBS 1543+593 gives rise
to a damped LyAlpha (DLA) absorption line in the spectrum of the background
quasar. DLA absorbers are the reservoirs of most of the observable neutral gas
mass in the Universe at higher redshifts, yet few have been directly matched
with galaxies so far. There is a clear need to seize the opportunity presented
by HS 1543+5921/SBS 1543+593, since a positive outcome would increase the
sample of well-resolved nearby DLA galaxies.
================================================================================
Proposal Category: GO
Scientific Category: QAL
ID: 8571
Title: Metallicity and D/H abundance in Low-z LyAlpha Absorbers
towards PG 1211+143
PI: J. Michael Shull
PI Institution: University of Colorado, Boulder

Our Cycle 7 STIS/G140M observations along the sightline toward PG 1211+143
reveal numerous LyAlpha absorption lines including 2 very strong LyAlpha
absorbers (cz = 15,300 and 19,550 km s^-1) with associated Si III absorption.
These are the first definite detections of metals in a low-z LyAlpha forest
cloud; simple photoionization models suggest metallicities in the range 1--10\
sim10^17 cm^-2 in each system, we should be able to detect deuterium LyAlpha
at 10--20 mAngstrom\ equivalent width, thereby testing models of D/H astration
as a function of IGM metallicity, an issue of cosmological significance. We
propose to obtain a 25-orbit (S/N ~ 25) STIS/E140M spectrum (1150-1740
Angstrom) at 10 km s^-1 resolution to detect or limit D I (LyAlpha) and to
measure metal absorption lines (C IV, Si IV, N V, C II, Si II) observable down
to below 10^-2 solar abundance (4 mAngstrom\ EW limit). This sightline is one
of two prime FUSE targets for long-duration exposures in the extragalactic D/H
program. FUSE will detect higher Ly-series lines and the Lyman break
(accurate H I column density) and measure key metal lines (C III Lambda977, O
VI Lambda1032,1038). Thus, the FUSE and STIS programs are highly
interdependent.
================================================================================
Proposal Category: GO
Scientific Category: QAL
ID: 8572
Title: Identifying Normal Galaxies at 1.3 < z < 2.5
PI: Lisa Storrie-Lombardi
PI Institution: California Institute of Technology

Studies of faint, distant galaxies have greatly advanced in recent years. It
is now possible to observe hundreds of galaxies out to z=1 and in the range 3
< z < 4.5, yet the redshift range 1 < z <3 remains largely unexplored.
Galaxies selected by MgII absorption lines detected in quasar spectra are
associated with normal galaxies up to redshifts z=1.2. We are extending this
work to z = 2.5. We are already obtaining deep ground-based optical and near-
infrared (VRIJK') images of fields around quasars with MgII absorbers. We
propose obtaining far-UV and CCD images of our QSO fields with STIS. The aims
of the observing program are: (1) Identify galaxies which produce MgII
absorption using the Lyman drop-out technique. The 912Angstrom\ Lyman break is
observed at 2100Angstrom\ -- 3200Angstrom\ for 1.3 < z < 2.5 so these galaxies
will be absent from far-UV images below 2000Angstrom. (2) Obtain high
resolution images to study MgII galaxy morphology. This can be accomplished
extremely efficiently with STIS 50CCD imaging. Our main scientific goals are:
(1) Find garden variety L^* galaxies at z ~ 2 when the Universe is 20-25\ as
were found in the Steidel & Dickinson (1995) sample of MgII absorbers at z <
1.2. (2) Study the evolutionary history of MgII selected galaxies. If they
are not typical L^* galaxies at z ~ 2 as they are at lower redshifts, we will
determine the redshift at which this change occurs.
================================================================================
Proposal Category: GO
Scientific Category: SF
ID: 8573
Title: Newborn Planets and Brown Dwarf Companions in IC 348
PI: Kevin Luhman
PI Institution: Harvard-Smithsonian Center for Astrophysics

We propose to use deep WFPC2 images to search for young giant planets and
brown dwarfs around ~100 low-mass stars and brown dwarfs in the nearby cluster
IC 348. This cluster's age, 1-10 Myr, makes it perfectly suited for detecting
such companions. While stars in star-forming regions such as Orion and Taurus
are still surrounded by thick proto-planetary disks, the stars in IC 348 are
old enough for most of the disks to have dissipated, yet young enough so that
the newly-formed brown dwarfs and giant planets are still very luminous. By
observing intrinsically faint, low-mass primaries, we should detect companions
down to 3 and 7 M_ Jup at separations of 90 and 30 AU. When the results of
this program are combined with other studies of planets at smaller separations
around older, more massive primaries, we will better understand the properties
of planetary systems as a function of primary mass and how they evolve from
birth to the age of the solar system. Furthermore, because low-mass stars and
brown dwarfs exist in such large numbers, this program is important in
determining the frequency of planetary systems in the universe.
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8574
Title: Proper Motions in Baade's Window
PI: Carl Grillmair
PI Institution: SIRTF Science Center/California Institute of Technology

We propose to obtain third epoch WFPC2 observations of a rich field in Baade's
Window. In just three orbits, we will be able to measure very accurate proper
motions for ~ 13,000 Galactic bulge stars down to V = 23. Such a large number
of stars, combined with color information, a relatively long baseline, and the
high spatial resolution of HST, will enable an unprecedented opportunity to
model the structure and dynamics of the Galactic bulge and bar populations. In
addition, by selecting stars on the basis of their proper motions, we will be
able to refine the color-magnitude distributions of stars in the bulge and the
bar, and thus the corresponding initial mass functions and chemical enrichment
histories.
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8575
Title: Leo A --- Evidence for the ``Delayed Formation of Dwarfs"
Scenario?
PI: Regina Schulte-Ladbeck
PI Institution: University of Pittsburgh

Did all galaxies form at high redshift, or was the formation of certain
galaxies delayed until recent (z<1) cosmological epochs? The delayed-formation
-of-dwarfs hypothesis discusses how the faint blue galaxies came to be and
where they are now: they represent copious dwarf galaxies that burst into
stars at 0.5 far, however, no galaxy has proven to have formed at these redshifts. Cycle
4 HST observations revealed that a delayed dwarf might be lurking in our own
backyard. The resolved stellar content of Leo A, a dIrr in the Local Group, is
consistent with star formation beginning only a few billion years ago.
However, the presence of an ancient stellar substratum cannot be ruled out by
these observations; the horizontal branch is at their detection limit, and
they point in a crowded region heavily populated with young stars which makes
the discrimination of horizontal branch stars impossible. We here propose to
exploit the capabilities of WFPC2 to obtain color-magnitude diagrams of Leo
A's halo. The clear signature of ancient stars lies in the horizontal branch,
and requires photometry that can only be done with very deep, high-resolution
images. Using synthetic CMDs, we will model the data to derive when Leo A
first started to form stars. This will allow us to determine unambiguously
whether Leo A is evidence for the ``delayed formation of dwarfs."
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8576
Title: The Star-Formation History of the Large Magellanic Cloud
PI: Tammy Smecker-Hane
PI Institution: University of California, Irvine

Accurately determining the star-formation rate (SFR) and chemical evolution of
the Large Magellanic Cloud (LMC) can give us a solid foundation for
understanding the evolution of intermediate-mass galaxies and, potentially,
the origin of ``faint blue galaxies" commonly found in redshift surveys. We
propose to continue a WFPC2 imaging survey of field stars in the LMC to obtain
color-magnitude diagrams (CMDs) that allow us to determine its SFR from 1 to
15 Gyr ago with unprecedented accuracy. Our goal is to measure 20\ SFR,
averaged over 1 Gyr intervals, at the 2 Sigma level in each region surveyed.
We imaged one region at the center of the bar and one region in the disk in
Cycle 7, and the resulting CMDs revealed clear differences in their evolution.
We now propose to image a third region, in the bar-disk interface, to begin to
quantify the evolution of the bar, disk, and halo of the LMC, and to define
the spatial extent of star bursts. Our project has generated the best CMDs
ever obtained for a galaxy other than the Milky Way. To derive the SFRs, we
compare observed and model CMDs using statistically rigorous techniques that
we have pioneered, and to surmount the age-metallicity degeneracy inherent in
CMDs, we have begun an ambitious project to directly measure stellar
abundances by obtaining spectra with ground-based telescopes of ~ 100 red
giant stars in each LMC region.
================================================================================
Proposal Category: GO
Scientific Category: SS
ID: 8577
Title: Ozone, Condensates, and Dust in the Martian Atmosphere
PI: Philip James
PI Institution: University of Toledo

We propose to utilize the unique capabilites of STIS and WFPC2 in order to
study the spatial and seasonal variations in ozone, condensates, and dust in
the Martian atmosphere. The data obtained promise to be critical in
addressing recent breakthroughs in understanding the basic radiative,
transport, and microphysical processes that provide for both long-term and
short-term balance within the global Mars climate system. Observations will
be obtained between late November 2000, when the solar elongation of Mars
first exceeds 50degrees, through June 2001 at which time the angular size of
the planet will be almost 21 arc seconds and the effective resolution at the
sub-earth point will be 15 km/pixel. The season on Mars during this period
is summer in the northern hemisphere, providing an opportunity to revisit the
equatorial cloud belt previously discovered by HST and further examine the
important interplay between water vapor and clouds during this season. These
observations are distinct from, but complementary to those that will be made
by the Mars Climate Orbiter.
================================================================================
Proposal Category: GO
Scientific Category: SS
ID: 8578
Title: First Spectroscopy of an Asteroid and its Satellite: (45)
Eugenia and S/1998 (45) 1
PI: William Merline
PI Institution: Southwest Research Institute

We recently made the first-ever discovery of a satellite of an asteroid from
the Earth, using adaptive optics (Merline et al. 1999a, 1999b). We propose
here to acquire the first separate, comparative, and simultaneous spectra of
an asteroid and its satellite. We will employ the UV-capabilities and high-
spatial-resolution properties of STIS to study (45) Eugenia, and its
satellite, S/1998 (45) 1, by obtaining medium-resolution spectra over the
range 2900--10300 Angstrom, using only two grating settings, on a single HST
orbit. We will determine whether the spectra, and hence surface compositions,
are similar or different in a parent-satellite pair, and to test hypotheses
concerning satellite production mechanisms. From the orbital parameters,
determined using our ground-based adaptive-optics images, we have already
determined that (45) Eugenia has a surprisingly low density of 1.2 g cm^-3.
We know the spectrum of Eugenia is a (Tholen) FC-type, which is similar to the
common C-types, but differs by the lack of a UV-band or UV-dropoff and by
subtle, but measurable differences in the spectral slope. Both the UV-region
and the existence of subtle absorption features in the near-IR (~ 0.9 Mum)
are diagnostic of the specific differences between F-, C-, and (Bus') X-class.
HST spectroscopy is the only way to separate the pair, because ground-based
adaptive optics is not available in the UV and cannot yet provide adequate
resolution in the visible.
================================================================================
Proposal Category: GO
Scientific Category: SS
ID: 8579
Title: A Search for the Martian Dust Belts
PI: Mark Showalter
PI Institution: NASA Ames Research Center

It has been long believed that Mars should be encircled by two faint rings of
dust, one originating from each of its moons Phobos and Deimos. Similar dust
rings have recently been associated with all the inner small moons of Jupiter.
On May 28, 2001, Earth will pass through Mars' equatorial plane within weeks
of its opposition, providing a unique opportunity to detect these rings via
direct imaging. Using WFPC2, we will be able to detect rings with normal
optical depths of sim10^-8, which is well within the range of the Martian
rings' predicted densities and 10--100 times fainter than the known Jovian
rings. The rings have been predicted to show some interesting dynamical
properties, including large asymmetries and inclinations. A positive
detection will enable us to test these predictions, serving as an effective
test of models developed to account for the faint rings of Jupiter and Saturn
as well. It will also provide both photometric and dynamical constraints on
the dust size distribution, enabling us to distinguish between several models
of the rings' dynamics and evolution.
================================================================================
Proposal Category: GO
Scientific Category: SS
ID: 8580
Title: Pre-Cassini/Huygens Studies of Titan's Surface,
Troposphere and Stratosphere
PI: Eliot Young
PI Institution: Southwest Research Institute

Titan, Saturn's largest satellite, has an opaque atmosphere in UV and visible
wavelengths due to aerosols and methane gas. We propose a data-dense suite of
observations to (a) map the three-dimensional distribution of methane and
aerosols in Titan's troposphere and stratosphere (up to 100 km), with the
possibility of detecting moving weather patterns, (b) provide a history of the
distribution of haze in preparation for Cassini and Huygens observations, and
(c) map Titan's surface albedo with unprecendented spatial resolution and
signal/noise. This proposal represents the most sensitive look at Titan's
troposphere to date. The results of this proposal (i.e., the distribution of
haze and methane) are important parameters in the planning of Cassini ISS and
VIMS observations. In addition, the detection of ephemeral clouds in the
troposphere (suggested from IR spectra) would help determine the direction of
tropospheric winds, a critical parameter in planning the Huygens probe tr
================================================================================
Proposal Category: SNAP
Scientific Category: CS
ID: 8581
Title: A search for low-mass companions to ultracool dwarfs
PI: Neill Reid
PI Institution: University of Pennsylvania

We propose to use the unparalleled resolution and sensitivity of WFPC2 to
search for very low-mass (VLM) companions to a complete sample of 120 late-M
and L dwarfs, drawn mainly from the 2MASS and SDSS surveys. Our primary goal
is to determine the multiplicity of M < 0.1 M_\odot dwarfs. In particular, we
aim to identify binary systems suitable for long-term astrometric monitoring
and mass measurement, and systems with cool, sub-1000K companions. With a
dynamic range of Delta m_I ~ 5 mag. for separations Delta > 0arcs3, these
observations are capable of detecting companions with mass ratios M_Sec /
M_Pri > 0.4. Most of our targets are at distances between ~10 and 40 parsecs.
Given a binary fraction and semi-major axis distribution similar to M dwarfs,
approximately 20\ are expected to be resolved. With detection limits extending
well below the hydrogen-burning limit to Gl229B-like temperature, these
observations, supplemented by ground-based imaging and spectroscopy, will
provide a definitive measurement of the binary fraction and mass-ratio
distribution in VLM dwarfs.
================================================================================
Proposal Category: SNAP
Scientific Category: QAL
ID: 8582
Title: UV Detectability of Bright Quasars in the Sloan Fields
PI: Wei Zheng
PI Institution: The Johns Hopkins University

He II Ly alpha absorption at 304(1+z) Angstrom\ is a far more sensitive tracer
of the intergalactic medium (IGM) than its H I counterpart. The recent
detections of such absorption in four quasars, albeit with limited data
quality and a small sample size, demonstrate the great potential of such a
probe. The lines of sight toward the majority of z~ 3 quasars are intercepted
by Lyman-limit systems, and these quasars' UV flux is cut off before reaching
the He II Ly alpha feature. As a result of the SDSS, a number of bright
(V<18), z>2.5 quasars are being identified. We propose a STIS snapshot survey
to confirm the UV detectability of about 50 such quasars, in order to select
the candidates for follow-up spectroscopic observations with STIS, COS, or
FUSE. Future high-quality HST spectra of these new quasars will enable us to
map the 70\ strict constraints on cold-dark-matter models of structure
formation in the universe and reveal the evolution of the IGM from the epoch
when the first generation of galaxies were formed down to z ~ 3.
================================================================================
Proposal Category: SNAP
Scientific Category: SS
ID: 8583
Title: Imaging Snapshots of Asteroids
PI: Alex Storrs
PI Institution: Space Telescope Science Institute

We propose to obtain WFPC2 images of the fifty largest main belt asteroids
that have favorable apparitions during cycle 9. The images will be searched
for companion bodies, as well as mineralogical variegation on the resolved
main bodies. Images in the F439W, F673N, F791W, F953N, and F1042M filters will
define the 1 micron Fe^2+ feature and the possible 0.7 micron hydration
feature. This will allow interpretation of compositional differences between
the primary and secondary bodies, as well as any brightness variations across
the disk(s) as being due solely to albedo. Because of the restriction that
moving target snapshots be done under gyro control, we expect to miss 1/3 of
the targets. We therefore request that each candidate be put in the snapshot
pool twice, and so request 100 ``targets'' for these fifty asteroids.
================================================================================
Proposal Category: GO
Scientific Category: COS
ID: 8584
Title: Calibrating the Metallicity Dependence of the Cepheid PL
Relation
PI: Robert Kennicutt
PI Institution: Steward Observatory

Uncertainty in the metal abundance dependence of the Cepheid PL relation
remains as one of the largest sources of systematic error in the Cepheid
distance scale and in the extragalactic distance scale as a whole. We
propose to directly test and calibrate the metallicity dependence of the PL
relation, by obtaining independent Pop II based distances to a sample of 6
Cepheid host galaxies with (Cepheid) metal abundances (0.2--2 Z_\odot), using
the tip of the red giant branch (TRGB) method. The TRGB method offers the
optimal combination of precision and metallicity insensitivity for this test.
When combined with currently available Cepheid and TRGB distances, these data
will provide: (1) A robust empirical calibration of the Cepheid metallicity
dependence; (2) Hard limits on the systematic error in H_0 from metallicity
effects; (3) Empirical constraints on theoretical models of Cepheids; (4)
Tight limits on other systematic errors in Cepheid distances as functions of
distance, stellar crowding, and extinction; (5) A valuable Pop II based cross-
check on the zeropoint of the Pop I distance ladder.
================================================================================
Proposal Category: GO
Scientific Category: COS
ID: 8585
Title: Cosmological Parameters from Type Ia Supernovae at High
Redshift
PI: Saul Perlmutter
PI Institution: Lawrence Berkeley Laboratory

HST can directly measure the cosmological parameters, Omega, Lambda, and thus
the curvature, Omega_k, using Type Ia supernovae (SNe Ia) as calibrated
standard candles. Observations of SNe Ia spanning a large redshift range are
key to decoupling Omega and Lambda. In Cycle 7 (and 7-NICMOS) we studied 12
SNe in the redshift range z~ 0.35--0.85; the forthcoming measurement of Omega
and Lambda is expected to have uncertainty ~11\ embarked on a program to
extend the redshifts to z~1.2, starting with 2 SNe. We here propose to
continue the painstaking work of obtaining a statistically significant sample
across this redshift range, by studying 2 more SNe at z~ 1.2, and filling in
the redshift gap with 3 SNe between z~ 0.85--1.0. Measurement of these
additional high redshift SNe will dramatically shrink the major-axis of the
error ellipse in the Omega_M---Lambda plane, and unambiguously determine
whether the universe contains a significant vacuum energy density. These data
will provide powerful constraints on SN Ia evolution and on absorption by
intergalactic ``gray'' dust; it would be very difficult for either evolution
or dust to alter corrected peak magnitudes in the same way as cosmology
predicts over the redshift range 0 observations will further give the first real limits on whether the universe
is spatially flat.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8586
Title: WFPC2 Observations of Astrophysically Important Visual
Binaries
PI: Howard E. Bond
PI Institution: Space Telescope Science Institute

This is a continuation of a Cycle 7-8 Long-Term project. The program consists
of annual or biannual WFPC2 observations of three visual binary stars that
will ultimately yield fundamental astrophysical results, once their orbits and
masses are determined. Our targets are the following: (1) Procyon (P=41 yr),
for which our first WFPC2 images yielded an extremely accurate angular
separation of the bright F star and its very faint white-dwarf companion.
Combined with ground-based astrometry of the bright star, our observation
significantly revised downward the derived masses, and brought Procyon A into
excellent agreement with theoretical evolutionary tracks for the first time.
The mass of Procyon B, however, implies a completely unexpected chemical
composition for the white dwarf, and now poses a sharp evolutionary puzzle.
With the continued monitoring proposed here, we will obtain masses to an
accuracy of better than 1\ dwarfs. (2) G 107-70, a close double white dwarf
(P=19 yr) that promises to add two accurate masses to the tiny handful of
white-dwarf masses that are directly known from dynamical measurements. (3)
pmbMu Cas (P=21 yr), a famous metal-deficient G dwarf for which accurate
masses will lead to the stars' helium contents, with cosmological
implications.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8587
Title: Stroemgren Photometry of Globular Clusters in M87:
Breaking the Age-Metallicity Degeneracy
PI: Patrick C\^ote
PI Institution: California Institute of Technology

A remarkable achievement of HST has been the demonstration that the globular
cluster (GC) systems of most, and possibly all, luminous galaxies show bimodal
distributions in broadband color and, by implication, age and/or metallicity.
Whatever its origin, this bimodality (which is observed in giant galaxies that
span a wide range in Hubble Type and local environment) must hold a
fundamental clue to the process of galaxy formation. Although several models
for the observed bimodality have been suggested (e.g., spiral-spiral mergers,
two phase collapse models, and hierarchical growth via dissipationless
mergers), a definitive test of these scenarios has proved elusive due to the
lack of reliable age estimates for the two GC populations in even a single
galaxy. In other words, the models make very different predictions regarding
the ages of the two GC populations, but the measured broadband colors suffer
from the well-known ``age-metallicity degeneracy" of old stellar systems. We
propose to break this degeneracy by using WFPC2 to obtain narrow-band
photometry in the Stroemgren uvby filters for ~ 10^3 GCs in M87, the
supergiant elliptical galaxy at the dynamical center of the Virgo cluster. Our
technique hinges on the ability of Stroemgren photometry to decouple the
effects of age and metallicity for large samples of GCs, and will provide the
first strong constraints on the various galaxy formation models.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8588
Title: Gamma-Ray Bursts and their Host Environments
PI: Andrew Fruchter
PI Institution: Space Telescope Science Institute

We propose to use the unique high-resolution optical and ultraviolet
capabilities of HST as well as the resolution and sensitivity of Chandra to
investigate the physics of gamma-ray bursts (GRBs) and the nature of their
host galaxies. Our approach is three-pronged: 1) rapid HST ultraviolet
spectroscopy and Chandra imaging obtained within two days of an outburst will
allow us to probe the physics of the relativistic fireball and the nature of
the ISM surrounding the GRB; 2) long-term optical monitoring of the optical
transient (OT) will permit us to test the hypothesis that GRBs are frequently
highly collimated and to determine whether supernovae underlie GRBs; 3)
Chandra and HST observations of "dark" GRBs will allow us to probe one of the
greater mysteries surrounding GRBs, the nature of the bursts without optical
counterparts. The ultraviolet and x-ray observations will also obtain the
metal and rmH_2 column densities to a number of OTs, as well as the extinction
law of the dust in these hosts. The late-time optical images will elucidate
the physics of the afterglow, as well as the morphology, structure and
luminosity function of the host galaxies. This comprehensive set of
observations will provide new insights into the astrophysics of GRBs and their
high redshift host galaxies.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8589
Title: Orbital Structure and Black Hole in NGC 3379
PI: Karl Gebhardt
PI Institution: UCSC/Lick Observatory

The stellar orbital structure and the mass of the central black hole in
dynamically hot galaxies are direct insights into their formation and
evolution---both of the black hole and galaxy. We propose to use gas
kinematics to determine the central black hole (BH) mass in NGC 3379 to high
accuracy. Detailed modeling including this BH mass and previous HST and
extensive ground-based data will measure the stellar orbital distribution
throughout the galaxy. Recent work suggests that elliptical galaxies tend to
have tangentially biased orbits near their centers, consistent with results
from BH binary simulations in galaxies. However, knowledge of the central BH
mass is one of the limiting factors for providing accurate measurements of the
orbital structure. In addition, this data will allow us to compare the mass
measured from gas to that measured from stellar kinematics using our previous
analysis. An urgent need in BH physics is cross checks between gas and stellar
BH masses, particularly in systems where the gas mass promises to be accurate.
NGC 3379 is a rare example of a system that lends itself to this comparison.
Finally, accurate BH masses are necessary ingredients to characterize the
relation, if one exists, between their masses and those of the host galaxy.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8590
Title: UV Imaging and Spectroscopy of Luminous Blue Compact
Galaxies from z=0 to z=1
PI: James Lowenthal
PI Institution: University of Massachusetts

Are Lyman Break Galaxies (LBGs) at redshift z~3 centrally-concentrated,
massive starbursts at the bottoms of deep potential wells of dark matter, or
isolated, irregular, low-mass starburst galaxies? One significant barrier to
deeper understanding of LBGs is the lack of available UV data on local star-
forming galaxies for comparison. To address that lack, we propose STIS FUV
imaging and spectroscopy of two well-defined samples of low-mass starburst
galaxies, one in the local universe (z<0.1) and another at intermediate
redshifts (0.2 < z < 0.7). Both samples show optical sizes, morphologies,
emission line widths, and luminosities comparable to those of LBGs at z=3, and
are therefore probably the best local analogs and testbeds for further study
of LBGs. Our main goals are to: (1) explore the morphologies, surface
brightness distributions, and half-light radii of nearby starforming galaxies
in the FUV, near Ly-alpha; (2) search for systematic differences among UV,
optical, and near-IR morphologies and structural parameters; (3) investigate
the intrinsic emission and absorption spectra near Ly-alpha\ of starbursting
dwarf galaxies, with special attention to Ly-alpha\ profiles and interstellar
and stellar photospheric absorption from Si II, O I, C II, Si IV, and C IV;
(4) measure their FUV-optical colors and dust extinction properties; and (5)
test the hypothesis that low-mass starbursts are the local counterparts of
LBGs.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8591
Title: The Smallest Nuclear Black Holes
PI: Douglas Richstone
PI Institution: University of Michigan

Small nuclear black holes are the last major unexplored part of BH parameter
space. We propose to search for the smallest BHs that HST can possibly
find. Past studies have concentrated on massive, distant spheroids,
overlooking many BH candidates on our own doorstep. The minimum detectable BH
mass can be driven down by nearly two orders of magnitude by focusing on the
nearest galaxies. We can easily reach down to 10^5 M(sun), the probable mass
of the ``first born'' objects that (in other cases) grow or merge up to the
quasar mass range. This strategy also favors disklike ``pseudobulges'', which
probably formed differently from classical spheroids and which therefore
provide a fresh perspective on the relationship between BHs and their
embryonic environments. Our complete sample of 20 nearby galaxies includes
all unstudied objects within 7.5 Mpc, brighter than M_B = -17, with well
defined, unobscured centers. STIS long-slit spectra will be used to measure
BH masses using both gas and stellar kinematics, comparing the results
whenever practical. Emission-line and broad-band images are sought to
characterize the central morphology of gas and stars. Of prime importance is
the maser galaxy NGC 4258, which provides a unique chance to calibrate both
stellar-- and gas-- dynamical BH masses against the impressively accurate
maser BH mass.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8592
Title: Pixel Microlensing of M87
PI: Joseph Silk
PI Institution: University of California, Berkeley

Resolving the nature of dark matter, at least some of which is baryonic, is an
urgent problem. If baryonic dark matter is associated with luminous baryonic
matter, MACHOs (massive compact objects) are the preferred candidate as
inferred from gravitational microlensing of LMC stars. Given the
uncertainties in the dynamical modeling of the dark components of the halo, a
broad mass range for MACHO candidates merits consideration, from 0.01 M_\odot
to 1 M_\odot. This includes the mass range of brown dwarfs and M dwarfs,
whose contribution towards the dark mass is unknown. We propose to use HST to
undertake a pixel microlensing study of M87 in order to: 1) probe the lower
end of the M87 IMF via star-star lensing, 2) possibly obtain the first
evidence of MACHOs in the halo of a galaxy other than our own, and 3) search
for intracluster MACHOs. The program is challenging, but very feasible, with
the HST. Over a period of 30 days and with half orbit exposures in each of two
colors at a rate of one per day, we will observe approximately 1-2 events per
day for a MACHO of mass 0.1 M_\odot, with about 5 points of the lightcurve
above 3Sigma. This provides a moderately high event significance threshold of
S/N >= 10. The key factor that makes this project possible with the HST is the
small pixel scale of the WFPC2, coupled with the small, stable PSF and
superior photometric capabilities.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8593
Title: Sakurai's Novalike Object: Real-Time Monitoring of a
Stellar Thermal Pulse
PI: Howard E. Bond
PI Institution: Space Telescope Science Institute

This is a continuation of a Cycle 7-8 Long-Term program. Sakurai's novalike
variable (V4334 Sgr) presents a ``once-in-a-lifetime'' opportunity for real-
time observations of a star undergoing a final helium thermal pulse. The star
rose from obscurity to become an 11th-magnitude, hydrogen-deficient red giant
in 1995-96, and currently it is undergoing episodes of atmospheric dust
formation which make it drop to quite faint magnitudes at random intervals.
If it follows the pattern of the similar object V605 Aql, it will soon begin
evolving back to high temperature. During the subsequent few years, it would
then begin to (re)-ionize its large, faint planetary nebula, and we should be
able to witness the re-establishment of a fast stellar wind as the effective
temperature increases. This is a Target-of-Oppurtunity proposal. When the
star does start to become hot again, we will start using STIS to monitor the
spectroscopic development of the star in the UV at regular intervals,
continuing over the next 3 Cycles. We will also use WFPC2 once a year to
monitor expansion of the ejecta. In combination with ground-based monitoring
(optical, IR, and mm), we will thus produce the first detailed case study of a
thermal pulse, as the star re-traces its evolution across the HR diagram from
the AGB to the planetary-nebula phase.
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8594
Title: H-deficient condensations in PNe -- a key to
discrepancies in abundance determinations
PI: Xiao-wei Liu
PI Institution: University College London

own and other galaxies rests on emission line nebulae. Our recent CNO
abundance determinations for PNe using optical recombination lines (ORLs) have
yielded abundances systematically higher than the `standard' values deduced
from UV/optical collisionally excited lines (CELs), with discrepancies
covering a wide range from 1--20. In the extreme case of NGC 6153, multi-
waveband analysis has yielded CNO and Ne abundances from ORLs which are all
about a factor of ten higher than the CEL values. Temperature fluctuations
and density inhomogeneities fail to explain all the available data. Instead
our analysis indicates that NGC 6153 may have experienced a recent ejection of
H-deficient knots, similar to those observed in the `born-again' PN A 30. We
propose to obtain deep STIS long-slit spectra for the well-resolved H-
deficient knots of A 30 and to search for such knots in NGC 6153. The data
will yield the spatially resolved temperature, density and ionization
structure of the knots in A 30, and, for the first time, accurate ORL C and O
abundances for them. The results will lead to a much better understanding of
the physics of such knots and their effects on abundance determinations. The
observations of NGC 6153 will allow us to test if the observed central peaking
of its ORL C and O abundances is a consequence of a central concentration of
similar
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8595
Title: Does the D/H Ratio Vary in Local Interstellar Gas?
PI: Meena Sahu
PI Institution: NASA/Goddard Space Flight Center

Measurements of the D/H ratio in the Local Interstellar Cloud (LIC) are
consistent with 1.5 +/- 0.1* 10^-5, while for other clouds within ~ 100 pc,
the measurement uncertainties are larger. Current data provide limited
information on whether the D/H ratio varies between the LIC and the other
clouds. We propose to determine if the D/H ratio varies, by high-precision
D/H measurements and by devising strategies to reduce both random and
systematic errors. STIS E140H & E230H mode (R~ 150,000) data will resolve the
velocity components and allow reliable determinations of component-to-
component variations. Two target white dwarfs (WDs) HZ 43 and GD 153 are
chosen because EUVE data show low H i column densities, thereby reducing the
probabilities of multiple velocity components and saturation of the D i
line. The WDs have pure-H atmospheres, so contamination of the interstellar
lines by photospheric metal lines is not an issue. Physically realistic NLTE
models will be used to accurately predict the WD Lyman-Alpha contributions.
HST-STIS, with its higher velocity resolution (compared to GHRS & FUSE), wider
wavelength coverage, and better scattered light corrections (compared to GHRS)
is the facility best suited for this project. We have demonstrated the
capabilities of STIS in our study of the G191-B2B sightline, which is the only
published STIS measurement of the D/H ratio to date.
================================================================================
Proposal Category: GO
Scientific Category: QAL
ID: 8596
Title: Environmental Pollution: The Outflow in the Archetypal
Galaxy-Quasar Pair NGC3067/3C232
PI: Max Pettini
PI Institution: Institute of Astronomy

Galactic-scale outflows are now known to be a common occurrence in star-
forming galaxies, in the nearby universe and at high redshift. These
superwinds have fundamental astrophysical implications for regulating star
formation, determining the evolution of the host galaxies, disseminating the
products of stellar nucleosynthesis over large volumes, and are probably
responsible for many of the metal absorption lines seen in QSO spectra. In
order to understand the physical process involved, we have been developing
detailed chemo-spectro-dynamical models which, however, suffer from a lack of
direct observational constraints. We propose to remedy this situation by
detecting the hot gas from NGC3067, a galaxy with concentrated nuclear star
formation giving rise to an outflow seen in X-rays, in STIS G140M spectra of
the background QSO 3C232. Although this is one of the best studied QSO-galaxy
pairs, there have been no high-resolution observations yet targeted at
absorption lines of highly ionized species, as requested here. In addition,
STIS spectroscopy of the nuclear regions of the galaxy will establish the age
and properties of the stellar population, so far only known from imaging data.
By bringing together X-ray, UV and optical data we will obtain the first
quantitative description of a galactic outflow, its relation to the star-
formation activity in the galaxy, and its effects on the interstellar and
intergalactic medium.
================================================================================
Proposal Category: SNAP
Scientific Category: AGN
ID: 8597
Title: The Fueling of Active Nuclei:, Why are Active Galaxies
Active?
PI: Michael Regan
PI Institution: Carnegie Institution of Washington

Accretion onto massive black holes is believed to be the energy source for
AGN. However, evidence for black holes in quiescent galaxies has also been
reported; why are these galaxies inactive? One possibility is that active
galaxies are better at providing fuel to the nuclear region than quiescent
galaxies. For the ISM to fuel a massive black hole it must lose significant
amounts of angular momentum. Although angular momentum can easily be removed
by stellar bars, recent ground-based studies of Seyferts show that the
fraction of bars in active galaxies is no higher than in normal galaxies.
Other possible fueling mechanisms such as ``bars-within-bars'' or nuclear
spirals cannot be investigated from the ground because they are relatively
small features in the ISM. Recent HST observations using optical - near-
infrared color maps to probe the morphology of the ISM at high resolution have
shown that the majority of Seyfert galaxies have nuclear dust spirals. We
propose to obtain WFPC2 snapshots of a sample of primarily quiescent galaxies
which we will combine with existing NICMOS images to form color maps to
determine if quiescent galaxies also have a large fraction of nuclear dust
spirals. This will allow us to determine if nuclear spiral arms are the
distinguishing feature that makes active galaxies active. Since the database
created will be invaluable for other studies of spiral galaxies, we are
waiving our proprietary period.
================================================================================
Proposal Category: SNAP
Scientific Category: AGN
ID: 8598
Title: Snapshot Survey of Extended OIIILambda5007Angstrom\
Emission in Seyfert Galaxies
PI: Henrique Schmitt
PI Institution: Space Telescope Science Institute

We propose a snapshot survey of narrow band OIIILambda5007Angstrom\ images for
a well defined sample of 88 Seyfert galaxies (29 Seyfert 1s and 59 Seyfert
2s), 18 of which already have data in the archive, selected from a mostly
isotropic property, the 60Mum flux. These data will be used: 1) to determine
the origin of the misalignment between the accretion disk axis and the host
galaxy plane axis, which can be due to mergers with other galaxies, or by the
self induced radiation warping; 2) to compare the size and shape of the NLR of
Seyfert 1s and Seyfert 2s, and to study the frequency of conically shaped
Narrow Line Regions (NLR) in Seyfert galaxies, which are usually unresolved
from ground-based observations; 3) estimate the importance of shocks to the
ionization of the NLR. We aim to provide a critical test of the applicability
and limitations of the Unified Schemes that currently are the framework for
understanding Seyfert galaxies and their luminous counterparts.
================================================================================
Proposal Category: SNAP
Scientific Category: GAL
ID: 8599
Title: A Census of Nuclear Star Clusters in Late-Type Spiral
Galaxies
PI: Torsten Boeker
PI Institution: Space Telescope Science Institute

Recent HST observations have revealed that many spiral galaxies have a
prominent star cluster in their dynamical center. Such a cluster can plausibly
have significant influence on the formation and/or evolution of the galaxy
bulge, which is an important new aspect in the ongoing discussion about the
origin of the Hubble sequence. While existing HST data indicate that nuclear
clusters can occur in spirals of all types, statistics for cluster frequency,
size, and luminosity as a function of Hubble type are incomplete. There is a
particular lack of data for late type spirals, because most HST studies were
biased towards earlier Hubble types. To fill this gap, we propose a WFPC2 I-
band snapshot survey of a well-defined sample of nearby, face-on spiral
galaxies of type Scd or later. Given the sizes of known nuclear clusters
(R_eff~ 0.2^ ), HST provides an order of magnitude contrast improvement over
ground-based imaging, crucial for an unambiguous identification of the
cluster. The data will also yield cluster sizes and unblended luminosities,
which are impossible to obtain from the ground. This program will be the first
systematic census of nuclear star clusters in late-type spirals. As such, it
will provide a valuable catalog for follow-up spectroscopy to study the
stellar populations, masses, and ages of these clusters, all of which are
important diagnostics for understanding their formation mechanism and possible
influence on the surrounding bulge.
================================================================================
Proposal Category: SNAP
Scientific Category: GAL
ID: 8600
Title: Dwarf Elliptical Galaxy Snapshot Survey III
PI: Henry C. Ferguson
PI Institution: Space Telescope Science Institute

We propose to extend our V and I snapshot survey of nearby dwarf elliptical
(dE) galaxies to include a sample of 30 bright dE (M_V < - 15.7) with
significant globular cluster (GC) populations. This survey will provide
important information on the globular cluster systems of such galaxies and the
properties of their cores and nuclei. The high resolution of HST allows us to
identify globular cluster candidates and classify more accurately a galaxy as
nucleated or non-nucleated. Our results from the Cycle 6 survey show that dE
have globular cluster specific frequencies (S_N) similar to those of giant
ellipticals. Nucleated dE have higher S_N than non-nucleated dE, and show a
trend of increasing S_N with fainter luminosities. We have also studied the
spatial distribution of the globular clusters and an interesting (lack of a)
trend is emerging. The globular cluster surface densities follow the
luminosity profiles of the underlying galaxies, on average, and there is no
segregation by luminosity. This is an interesting result, if confirmed,
because the dynamical friction timescales for dE galaxies are significantly
shorter than a Hubble time. With better statistics, analysis of the cluster
spatial distribution can place constraints on the ages of the clusters and the
dark matter, and offer tests of the universality and evolution of the globular
cluster luminosity function.
================================================================================
Proposal Category: SNAP
Scientific Category: GAL
ID: 8601
Title: A Snapshot Survey of Probable Nearby Galaxies
PI: Patrick Seitzer
PI Institution: University of Michigan

The census of galaxies in the Local Volume of space is very incomplete,
particularly at the faint end. We propose to continue our very successful
snapshot survey to use the high spatial resolution of HST to determine whether
selected galaxies are nearby on the basis of resolution into stars, and the
magnitudes and colors of the brightest stars. In the first 2 months of the
cycle 8 proposal, data was obtained on 18 candidates, and 15 (83 \ on the
magnitudes of the brightest stars. We are rapidly increasing the number of
confirmed galaxies within 4 Mpc. Our sample is chosen from the survey by team
members Karachentsev & Karachentseva (KK98) of some 260 nearby dwarf galaxy
candidates. Our F606W & F814W snapshot survey will concentrate on 125
unobserved candidates. One HST orbit per galaxy results in a distance from
the magnitude of the tip of the red giant branch (TRGB) and is sufficiently
deep to identify the brightest stellar population if the galaxy is within 4
Mpc. Keck, VLT, and other large telescopes will be used for spectroscopic
follow-up for abundances and kinematics. The survey has already discovered
two possibly isolated dwarf galaxies not associated with any galaxy or group.
Since the sample to be observed is chosen from an all sky sample, we will be
able to determine if there is a significant number of such isolated dwarf
galaxies.
================================================================================
Proposal Category: SNAP
Scientific Category: HS
ID: 8602
Title: A Snapshot Survey of the Sites of Recent, Nearby
Supernovae
PI: Alex Filippenko
PI Institution: University of California at Berkeley

During the past few years, the Lick Observatory Supernova Search (LOSS) and
the Beijing Astronomical Observatory Supernova Search (BAOSS) have found a
total of 76 supernovae (SNe), 62 of them in relatively nearby galaxies (cz <=
6000 km s^-1). Most of the nearby objects were discovered before maximum
brightness. All have follow-up photometry and spectroscopy; they include some
of the best-studied SNe to date. We propose to conduct a WFPC2 snapshot survey
in V and I of the sites of the nearby SNe, which have precisely known
positions, to obtain high-resolution information on their local environment.
For example, we will see whether SNe of a given kind tend to occur close to
star clusters, or in dusty regions, or in old (red) stellar populations. This
will give important clues to the nature of their progenitor stars, with
ramifications for many areas of astronomy (e.g., stellar evolution,
nucleosynthesis, cosmology). For some of the most recent or unusually long-
lived SNe, the new HST data will provide late-time photometry that is
superior to what we can obtain from the ground. This proposal is similar, but
complementary to, our archival proposal in which existing HST images from
other programs are used to glean information about the environments of SNe.
To make the data readily available to other researchers studying these SNe, we
waive the entire proprietary period.
================================================================================
Proposal Category: SNAP
Scientific Category: HS
ID: 8603
Title: Secular changes in the temperatures and radii of extreme
helium stars
PI: Simon JEFFERY
PI Institution: Armagh Observatory

Extreme helium stars (EHEs) are luminous stellar remnants evolving rapidly to
become white dwarfs. They represent an important stage in the evolution of at
least some low-mass stars, and are closely related to the R Coronae Borealis
variables. Models do not agree about their origin, nor about what fraction of
normal stars pass through this phase, in which the stars have been completely
stripped of their outer layers. The models do predict that EHEs are
contracting and provide rate predictions and evolutionary lifetimes. First
and second epoch IUE observations have shown that these contraction rates can
be measured. We propose HST/STIS observations of 15 EHEs which, together with
IUE data, will give a 20-year baseline of ultraviolet spectrophotometry. These
observations will provide effective temperatures and angular radii with an
internal accuracy for individual stars of $~1\ precision which cannot be
achieved from optical or other diagnostics. From these measurements we will
measure precise contraction rates for a larger sample of targets and obtain
direct tests of the evolution models. Building on the IUE archive, the higher
quality of HST data will provide a foundation dataset for establishing
fundamental quantities (e.g. extinction) and for studying evolutionary changes
in EHEs into the next century and beyond.
================================================================================
Proposal Category: SNAP
Scientific Category: SP
ID: 8604
Title: Stellar Populations Across the Small Magellanic Cloud:
History and Structure
PI: Eline Tolstoy
PI Institution: European Southern Observatory

The Small Magellanic Cloud (SMC) is an extraordinary galaxy. It is the nearest
example of a low metallicity, star-forming dwarf irregular, contains a wide
range of stellar ages, and is distorted by interactions with the Milky Way and
its close companion, the Large Magellanic Cloud. We propose to investigate the
structure and evolutionary history of the SMC by obtaining a series of 50
three-color SNAPshots with WFPC2 of selected SMC regions. With this polling
of SMC field star properties, we will produce color-magnitude diagrams (CMDs)
in the U, V and I bands which will reach V~23.5 in regions too crowded to be
observed accurately from the ground. We will use these data for investigations
of two major topics: (1) the star formation history of the SMC, by
quantitative matching between models and data using a sophisticated numerical
approach which properly accounts for errors and other uncertainties. (2) the
structure of the SMC along our line of sight. The galaxy is thought to be
considerably distended in this direction and we will put constraints on this
from the width of the observed lower main sequence. In addition, by obtaining
accurate photometry for about 100,000 stars in each region, our CMDs will
provide an excellent basis for comparisons with evolutionary tracks of low
metal stars in the few solar masses range.
================================================================================
Proposal Category: GO
Scientific Category: AGN
ID: 8605
Title: Stellar-Dynamical Measurements of the Black Hole Masses
of Reverberation-Mapped AGN
PI: Gary Bower
PI Institution: National Optical Astronomy Observatories

The broad emission line regions of 20 AGN have been successfully reverberation
mapped in intensive international monitoring campaigns, allowing model
dependent determinations of the central mass. This determination depends on
the hypothesis that the dynamics in this gas are dominated by gravity,
consistent with the detection of the expected Keplerian decline in velocity
with radius in the best studied case (NGC5548). However, when normalized by
the bulge mass of the host galaxy, the central masses in these 20 AGN are over
an order of magnitude less massive than the compact dark masses found in
normal galaxies. If the masses determined by reverberation mapping can be
independently verified, this technique could potentially be used to measure
the evolution in the masses of the population of supermassive black holes over
cosmic time and determine these masses in radio-quiet and radio-loud AGN
spanning a huge range in luminosity. We therefore propose to use STIS to
measure the stellar dynamics in the type 1 Seyfert nucleus in NGC3227, in
which the measurements will be the most straightforward by far. If the
reverberation mapped mass is correct, we will see its dynamical signature in
these new data.
================================================================================
Proposal Category: GO
Scientific Category: AGN
ID: 8606
Title: Determining the Nature of the Variable Absorption in AGN:
Monitoring NGC 3783 with HST and Chandra
PI: D. Michael Crenshaw
PI Institution: Catholic University of America, STIS Science Team

About 60\ characterized by high ionization (C IV, N V), moderate widths (30 --
300 km s^-1), significant outflow velocities (up to 2500 km s^-1), and
variability on time scales as small as days. Seyferts with UV absorption also
show variable X-ray ``warm absorbers'', characterized by O VII and O VIII
absorption edges, which suggests a common origin. The frequent occurrence of
intrinsic absorption indicates that an important component has been missing
from our overall picture of active galaxies. To understand the nature and
origin of this component, and thereby use it as a probe of the active nucleus,
we must know its location, physical conditions, and kinematics. Variability
monitoring is the key to understanding the absorbers, by providing their
radial locations, densities, and evolution in ionization, column density,
velocity, and coverage of the inner active nucleus. However, our search for
the nature of the absorption has been hampered by the lack of an intensive UV
and X-ray monitoring campaign at high spectral and temporal resolutions.
HST/STIS and Chandra are ideal instruments for this pursuit, and NGC 3783 is
an ideal target, because it shows extremely variable absorption and rapid
continuum variability in both the UV and X-rays.
================================================================================
Proposal Category: GO
Scientific Category: AGN
ID: 8607
Title: Completing the Local AGN Inventory: The AGN Content of
Composite Nuclei
PI: Luis Ho
PI Institution: Observatories of the Carnegie Institution of Washington

Knowledge of the local space density of AGNs is of fundamental importance to a
number of astrophysical problems. A significant fraction of nearby galaxies
have nuclei whose spectra are intermediate between those of LINERs and nuclear
starbursts. These ``transition objects'' may be composite systems that contain
both a central AGN and circumnuclear star formation. We will test this
hypothesis by using STIS to obtain spatially-resolved optical spectra of a
well-defined sample of 15 nearby (<= 17 Mpc) transition nuclei selected from
the extensive ground-based survey of Ho, Filippenko, and Sargent. The
physical origin of these objects affects the census of AGNs in nearby
galaxies, the nature of nuclear star formation, and the possible connection
between starburst and AGN activity. We will use the G430L and G750M gratings
to cover the most important diagnostic emission lines in order to search for
line-ratio variations across the nuclear region. If the two-component model
for transition nuclei is correct, we expect the spectra to change from H II\
region-like to AGN-like as the center of the galaxy is approached. We will
also use the high-resolution spectra to search for weak broad H\al\ emission,
the classical signature of AGN activity, at a level of sensitivity far greater
than is possible from the ground. Finally, the spectra will provide a rich
source of nebular diagnostics to systematically study the physical properties
of nuclear H II\ regions.
================================================================================
Proposal Category: GO
Scientific Category: AGN
ID: 8608
Title: Simultaneous HST, Chandra, and FUSE Spectroscopy of NGC
4151
PI: Gerard Kriss
PI Institution: Space Telescope Science Institute

Absorption by warm, ionized gas at UV and X-ray wavelengths is proving to be a
common feature in Seyfert 1 galaxies, showing its presence in well over half
the galaxies observed. In some cases, like NGC 4151 and NGC 3516, the
absorption is seen over a wide range of ionization states, and it is optically
thick at the Lyman limit, thick enough to potentially collimate the ionizing
radiation in these objects and produce ``ionization cones" visible in emission
-line images. Thus understanding this warm absorbing gas and its origin may
help us to understand how radiation is collimated in AGN, and it may provide
additional clues to the differences and similarities between Type 1 and Type 2
AGN. The proximity and brightness of NGC 4151 make it a key object for
understanding the structure of AGN. We propose to obtain simultaneous
spectroscopy of the absorbing gas in NGC 4151 using the STIS echelle modes on
HST, FUSE, and Chandra. These observations will allow us to determine the
ionization states of each of the 8 kinematic components present in the
absorbing gas in NGC 4151, and to resolve the persistent discrepancies between
the gas columns inferred for the UV and X-ray absorption over the past two
decades. The simultaneity will avoid any ambiguity due to the known
variability in the UV and X-ray absorption.
================================================================================
Proposal Category: GO
Scientific Category: AGN
ID: 8609
Title: Host galaxy luminosities of the most luminous QSOs
PI: Lance Miller
PI Institution: Oxford University Department of Physics

What are the factors that determine whether a galaxy is host to a luminous
QSO? Recent evidence indicates that host galaxy spheroid mass is a key
factor: we want to test the relationship between host galaxy and QSO
luminosity at the highest feasible QSO luminosities by measuring the
luminosities and profiles of host galaxies for QSOs with -25.8 > M_V > -27.6.
Current data in this area are conflicting, and we aim to make a definitive
experiment that takes careful account of problems caused by extended line or
continuum emission around QSOs, relativistic beaming, gravitational lensing
and galaxy interactions.
================================================================================
Proposal Category: GO
Scientific Category: AGN
ID: 8610
Title: A Black Hole Offset from the Host Galaxy Mass Center?
PI: Carole Mundell
PI Institution: University of Maryland

It has been suggested that the central regions of many galaxies are unlikely
to be in a static steady state, with instabilities caused by sinking
satellites, the influence of a supermassive black hole or residuals of galaxy
formation, resulting in the nuclear black hole orbiting the galaxy center. The
observational signature of such an orbiting black hole is an offset of the
active nucleus (AGN) from the kinematic center defined by the galaxy rotation
curve. This orbital motion may provide fuelling of the AGN, as the hole
`grazes' on the ISM, and bent radio jets, due to the motion of their source.
The early type (E/SO) Seyfert galaxy, NGC2110, with its striking twin, `S'-
shaped radio jets, is a unique and valuable test case for the offset-nucleus
phenomenon since, despite its remarkably normal rotation curve, its
kinematically-measured mass center is displaced both spatially (260 pc) and
kinematically (170 km s^-1) from the active nucleus, as seen both in optical
and radio studies. However, the central kinematics, where the rotation curve
rises most steeply, are inaccessible with ground-based resolutions. The
proposed WFPC2 imaging and long-slit STIS spectroscopy of NGC 2110 will enable
determination of the structure and kinematics of gas moving in the galactic
potential on subarcsecond scales and investigate the origin of the off-set
nucleus.
================================================================================
Proposal Category: GO
Scientific Category: COS
ID: 8611
Title: UV Observations of Nearby Type Ia Supernovae
PI: Peter Nugent
PI Institution: Lawrence Berkeley National Laboratory

Two independent research groups have presented compelling evidence for an
accelerating universe from the observation of high-redshift Type Ia supernovae
(SNe Ia). These findings have such important ramifications for cosmology that
every effort must be made to throughly test the calibrated standard candles on
which they are based, improve upon our understanding of the underlying physics
of the SN Ia explosion mechanism and attempt to constrain or determine their
progenitors. Here we propose to obtain STIS/CCD UV spectra of five nearby
(0.02 < z < 0.08) SNe Ia in the Hubble Flow. The spectra will be taken at
weekly intervals over a range in time starting slightly before maximum light
and extending to +30 days. These observations will accomplish the following
three goals: (1) Calibration of the rest frame UV light curves of SNe Ia and
an assessment of their potential use as distance indicators through UV light
curve shape analyses. (2) Improvement in our understanding of the physics of
SNe Ia, metallicity/evolutionary effects and correlations between peak
brightness and UV spectral features. (3) Calibration of the SNe Ia previously
observed by HST at high-redshift. For the z > 0.8 SNe Ia observed by both the
Supernova Cosmology Project and the High-Z Supernovae Search Team this data is
crucial for proper cross-filter k-corrections and calibration of the supernova
photometry.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8612
Title: Boron in the Lithium-Rich K-Giants: A Critical Test of
Deep Stellar Mixing Versus Brown-Dwarf Ingestion
PI: Ramiro de la Reza
PI Institution: Observatorio Nacional

We will observe the B I 2500Angstrom\ lines in four Li-rich K-giants using HST
with STIS/G230M in order to test two different evolutionary scenarios invoked
to explain the high Li abundances: the cool bottom process (CBP) versus the
possible accretion of brown dwarfs/planets. This test utilizes the two
following properties of boron: among the three light elements (Li, Be, and B)
which are easily destroyed in stars by (p,Alpha) reactions, B is the least
fragile to nuclear destruction. In addition, unlike Li which can be created
under certain conditions in stellar mixing, B can only be destroyed. The
hypothetical mixing mechanism, CBP, produces Li by introducing deeper mixing
to hotter layers such that ^7Li is created via ^3He(alpha,Gamma)^7Be(e^-,anti-
Nu)^7Li. A by-product of CBP is the total destruction of pre-existing Be and
B. If B I is absent from the spectra, we will prove that deep mixing has
occurred. In an accretion scenario, the increase in the Li abundance caused
by the deposition of fresh material onto the red giant from a substellar mass
companion will also result in an increase in the Be and B abundances. Because
B is more robust to nuclear burning than Be, as well as initially being 20
times more abundant, spectroscopy of the B I lines will provide a solid and
definitive test of whether the process that creates these chemically peculiar
giants is a new type of internal mixing, or the ingestion of a substellar mass
companion.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8613
Title: Coordinated Observations of Stellar Flares on AD Leo
PI: Suzanne Hawley
PI Institution: University of Washington

We will obtain high resolution HST/STIS spectra of the dMe star AD Leo during
periods of quiescence and during flares to study the physics of atmospheric
heating in flare stars. The HST observations will form an essential part of a
large, coordinated observing campaign including FUSE, EUVE, and ground-based
observations (both multicolor photometry and high resolution optical
spectroscopy). The STIS spectra, in combination with data from the other
satellites, will allow us to determine the structure (during quiescence) and
evolution (during flares) of the temperature and density in the corona,
transition region, and chromosphere. These data will provide strong
empirical constraints on our current generation of flare evolution models.
The uniquely high spectral resolution of the STIS data will also allow us to
directly observe the dynamic effects of the chromospheric shocks that are
predicted by the models. In addition, we will search for significant red-
shifted emission in the hydrogen Lyman-Alpha line during the flare rise phase,
which is a signature of an energetic proton beam. The existence and role of
proton beams in both solar and stellar flares is currently a subject of
considerable debate.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8614
Title: NUV Extension of the Arcturus Project: Probing the Onset
of Chromospheric Heating
PI: Kenneth Hinkle
PI Institution: National Optical Astronomy Observatories

Two stars have multi-wavelength atlases at resolutions (R>= 100,000) high
enough to resolve dynamically interesting line structure: the Sun (G2 V) and
Arcturus (K2 III). These canonical atlases provide an astrophysical test bench
for studying the effects of temperature, gravity, and metalicity in cool
stars. We have produced high resolution spectral atlases of the Sun from 22
Mum through the visible, as well as a high resolution spectral atlas of
Arcturus from 5 Mum through 0.9 Mum. These atlases are widely used for line
identification, calibrating atomic data, testing model atmospheres, studying
stellar granulation, etc. We are currently finishing a major new digital atlas
of the Sun and Arcturus from 3600--9000 Angstrom\ at R=150,000 (to be
published next year as an ASP monograph). We propose to extend the spectral
coverage of these atlases down to 2124 Angstrom, using existing STIS spectra
of Alpha Cen A (as a solar proxy) and new STIS observations of Arcturus. The
NUV spectrum is astrophysically important because it encompasses the
transition from the photosphere through the temperature minimum into the
chromosphere. Modeling the spectroscopic transition from absorption to
emission lines will provide important semi-empirical constraints on the poorly
understood nonradiative heating processes that give rise to chromospheres in
evolved stars.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8615
Title: Ultraviolet Spectroscopy of R Coronae Borealis Stars --
Broad Lines from an Accretion Disc?
PI: David L. Lambert
PI Institution: University of Texas at Austin

STIS spectra of three R Coronae Borealis (RCB) stars will provide novel data
on hot gas near these stars; such data can be obtained only from HST. RCBs
are hydrogen-deficient and fade at unpredictable times as a carbon soot cloud
obscures the star. Optical spectra taken when a star has faded reveal an
emission line spectrum containing sharp (FWHM ~eq 15 km s^-1) and broad (FWHM
~eq 250 km s^-1) lines. The lattter are of much higher excitation than the
former. For R CrB, it has been suggested that the broad lines arise from an
accretion disk around a compact secondary. These optical lines are visible
only during the infrequent extreme fadings of a RCB. Although IUE spectra
reveal high-excitation emission lines at maximum light, the IUE spectra lack
the spectral resolution to distinguish broad from sharp lines. STIS spectra
will resolve the broad-line from a sharp-line component, and, in the case, of
R CrB, where repeat visits are requested, be used to search for velocity
variations as the companion orbits the RCB. In addition, the line intensity
ratios will provide new estimates of the physical conditions of the gas
emitting the broad lines. This proposal may help to answer the question -- How
are RCBs formed? And this answer may show that, although RCBs are rare, many
low mass stars evolve through the RCB on their path to extinction as a white
dwarf.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8616
Title: Masses of Pre-Main Sequence Binaries
PI: Michal Simon
PI Institution: State University of New York

We propose to continue to map the orbits of young star binaries in the Taurus
and Ophiuchus star forming regions. Our goal is to measure their masses
dynamically. This is important because there are still no low mass young stars
with reliably known masses so calculations of their evolution to the main
sequence are uncalibrated.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8617
Title: Ultraviolet Spectroscopy of Hot Horizontal-Branch Stars
in the Globular Cluster M13
PI: Bradford Behr
PI Institution: California Institute of Technology

Blue horizontal-branch (BHB) stars in the metal-poor globular clusters M13 and
NGC 6752 have recently been found to exhibit remarkable metallicity
enhancements and helium depletion relative to the canonical cluster
composition. These abundance anomalies are most likely due to diffusion
processes --- radiative levitation of the metals, and gravitational settling
of helium --- in the stable radiative atmospheres of these hot stars. With
available ground-based facilities, we have observed stars in M13 as hot as
19000 K, but beyond this point we are constrained by low V- and B-band flux
and an insufficient number of visible-wavelength spectral lines. We therefore
propose HST/STIS spectroscopic observations in the wavelength range 1700--3100
Angstrom\ to extend the abundance measurements in M13 to yet hotter stars.
Such measurements will provide a new and important confrontation between
theory and observations of the diffusion mechanisms, and will also offer
insights into poorly-understood aspects of CMD morphology, including the BHB
`gaps' and overluminous BHB stars observed in many clusters.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8618
Title: FGS parallaxes of magnetic CVs
PI: Klaus P. Beuermann
PI Institution: Universitaets-Sternwarte Goettingen

Trigonometric parallaxes of cataclysmic variable (CVs) are needed to obtain
reliable information on luminosities, accretion rates, and on radii and masses
of the stellar components. They are also needed to derive the space density,
an important ingredient for theories of CV evolution. Photometric and
spectroscopic parallaxes of CVs are notoriously uncertain because the stellar
components have properties different from single field stars. Obtaining
trigonometric parallaxes of CVs will allow us to understand to what extent the
other methods are applicable to CVs and why they fail in certain cases.
Trigonometric distances are also needed for those CVs to which the other
methods can not be employed, e.g. because the secondary star, serving as a
standard candle, is not detectable. In summary, trigonometric parallaxes are
essential to our understanding of CVs. We propose to obtain accurate
trigonometric parallaxes of three magnetic cataclysmic variables (CVs) which
are among the brightest of their class, are not accessible to other methods of
distance determinations, and have largely defied physical interpretation so
far. We will: (1) clarify the nature of the enigmatic system EX Hya; (2)
measure the radius (and thereby the mass) of the white dwarf in EF Eri, obtain
tight limits on the magnitude of its (near-)degenerate secondary star,
determine the mass-transfer rate supposedly driven by gravitaional radiation;
and (3) decide on the nature of AH Men, one of the brightest long-period
(probable) Intermediate Polars.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8619
Title: Critical spectroscopic variations in Eta Carinae
PI: Kris Davidson
PI Institution: University of Minnesota

The very massive, unstable, persistently enigmatic star Eta Carinae has
implications for several branches of astrophysics. While HST has produced a
series of remarkable discoveries concerning this object, the nature of the
central star remains elusive. Now, however, recent developments offer, for
the first time, an approach that can settle certain long-standing questions
which have been obstacles to understanding this unique object. A 5.5-year
spectroscopic and X-ray cycle has been confirmed. STIS now provides the most
promising and very likely the only way to test whether Eta Car is a 5.5-yr
binary system. If it is, STIS will also allow us to constrain the parameters,
needed to assess the companion star's possible role in past outbursts and
ejecta. If the data conflict with binary models, then the 5.5-yr effect is
probably a thermal cycle which will give novel information about the star's
structure. In addition to the periodicity, a large, almost unprecedented
brightening, first noticed in HST data, has occurred since 1997 and merits
followup observations. We sense a breakthrough in the periodicity and the
brightening, if Eta Car can be observed repeatedly with STIS through the
current 5.5-year period, 1998.0---2003.5.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8620
Title: Taking a glance at the beating heart of 4 Draconis
PI: Boris T. Gaensicke
PI Institution: Universitaets-Sternwarte Goettingen

4 Dra is a unique triple system containing a magnetic cataclysmic variable (AM
Her-type) and an M3 III giant. Even though the M-giant completely dominates
the optical emission of the system, we can learn much from 4 Dra about the
accretion physics in and the evolution of AM Her stars, because: (a) 4 Dra is
the second brightest AM Her star in the ultraviolet, (b) 4 Dra is one of the
very few cataclysmic variables with a good HIPPARCOS parallax (d~180 pc), and,
in addition, (c) 4 Dra is so far the only bright CV for which an estimate of
the age, ~10^8 yrs could be derived. We propose an in-depth HST/STIS echelle
study of the AM Her star in 4 Dra. Our scientific goals are twofold. (1) We
will derive the fundamental properties of the accreting magnetic white dwarf,
such as its photospheric temperature, the temperature and the size (lateral
extent) of the accretion-heated pole cap, and the chemical composition of the
accretion-enriched atmosphere. (2) We will use the HST/STIS echelle spectra
for Doppler mapping of the UV line emission. The HST maps of LineCIV1550 and
LineHeII1640 emission will probe the velocity field and ionization structure
in the complete accretion flow, including the irradiated face of the donor
star, the ballistic gas stream from that star to the white dwarf
magnetosphere, the threading region between the stream and magnetosphere, the
magnetically controlled flow down to the standoff shock, and the surrounding
heated regions at the white dwarf surface.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8621
Title: The Galactic Abundance Gradients of Boron and Iron
PI: David L. Lambert
PI Institution: Department of Astronomy, University of Texas

This proposal aims to provide the first measurement of the Galactic abundance
gradients for Boron and Iron. Boron abundances will be obtained for 5 B-type
stars (with Galactocentric distances between 4--15 kpc) from the B iii
2066Angstrom\ line. Optical spectroscopy of these (and other B-type) stars has
yielded abundance gradients of -0.07 dex kpc^-1 for N & the Alpha-elements
(O,Mg,Si). Determination of Boron abundances require UV spectra and HST/STIS.
It is significant that stellar nucleosynthesis which is the leading source of
oxygen (via Type II SN) is unlikely to be a major contributor to B synthesis
(spallation being the leading candidate). Hence, a measurement of the B
abundance gradient provides novel information on the gradient of cosmic ray
flux in the Galaxy. The same STIS spectra will also provide Fe iii lines
that will be used to obtain the first estimate of the present abundance
gradient for iron (thought to originate predominantly in Type I SN). Recent
advances in modelling the chemical evolution of the Galactic disk have led to
definite predictions of the spatial variation of the Alpha/Fe ratio in
competing Galaxy formation scenarios, viz. the biased infall and biased
outflow models. This study should yield differential Fe abundances accurate
to +/-0.1 dex -- which will allow a Alpha/Fe gradient to be compared directly
with theory, as a critical test of formation models.
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8622
Title: The Interstellar Isotopic Ratio of Boron toward Omicron
Persei and Nearby Sight Lines
PI: David L. Lambert
PI Institution: University of Texas at Austin

The isotopic ratio ^11B/^10B will be determined for diffuse interstellar
material along lines of sight to 40 Persei, o Persei, Zeta Persei, and X
Persei that pass close to the star-forming region IC 348. High-resolution
spectra of the Li, i 6707Angstrom\ line toward o and Zeta Per show remarkably
different isotopic ratios for lithium. Particularly striking is the ratio
^7Li/^6Li ~eq 3 for o Per while Zeta Per shows a quasi-solar (~eq 10) ratio.
The significance of the very low ratio for o Per is that it is essentially the
value predicted for production by relativistic cosmic rays through spallation
reactions; it is the only interstellar or stellar measurement that approaches
this theoretical value. This discovery provides a novel opportunity to measure
the isotopic B ratio of gas with a Li concentration dominated by spallation
induced by relativistic cosmic rays. Feasibility of isotopic measurements has
been demonstrated by our GHRS observations of the interstellar B, ii
1362Angstrom\ resonance line that provided the first extra-solar measurement
of the ratio. Comparison of the observed and predicted isotopic B (and Li)
ratio will test the relative importance of B synthesis by cosmic rays and Type
II supernovae, and test proposals that invoke high-fluxes of high-energy
particles in star-forming regions as major players in light element synthesis.
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8623
Title: HST, Chandra, and FUSE Studies of Interstellar Material
toward HD 24534 (aka X Persei)
PI: Theodore P. Snow
PI Institution: University of Colorado

We are proposing new HST/STIS high-resolution UV spectroscopic observations of
the reddened star HD 24534 (aka X Persei), in order to: (1) establish accurate
gas-phase column densities for elements other than carbon and oxygen (for
which high-quality data already exist), for the purpose of deriving (in
conjunction with FUSE and Chandra observations) absolute depletions of
several key elements; and (2) further pursue molecular abundances toward this
star, to supplement HST/GHRS data obtained earlier which showed that this line
of sight supports a rich chemistry. The depletion work will focus on
magnesium, silicon, and iron, while the molecular observations will entail
searches for vibrationally excited H_2, an important indicator of cloud
physical conditions; and sulfur- bearing species (such as SO, CS, and SH),
which represent an important unknown in current models of interstellar cloud
chemistry. HD 24534 is the best possible target for this work, because it is
the brightest star available that lies behind a translucent line of sight with
high molecular abundances, and because it is also an x-ray source whose
spectrum is ideally suited for the measurement (through x-ray absorption and
scattering) of total (gas plus dust) abundances in the line of sight. This
will be the first line of sight for which depletions have been determined
independent of any assumed ``cosmic'' abundance standard such as the sun or
other stars.
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8624
Title: Imaging and Spectroscopy of Dusty Circumstellar Disks
PI: Alycia Weinberger
PI Institution: University of California Los Angeles

Understanding the properties and evolution of dusty disks in the circumstellar
environments of young stars is a key element in furthering our concepts of the
formation mechanisms of extra-solar planetary systems. In the past year, the
advent of NICMOS and STIS coronagraphy has given rise to the first reflected
light imaging, other than for Beta Pic, of dusty circumstellar disks with
spatially resolved morphological structures. NICMOS has taken a first step in
imaging these new disks, elucidating their geometries, morphologies, and bulk
photometric properties, while increasing the number of such known systems from
one to half a dozen. These dusty disks vary in physical size by over two
orders of magnitude and exhibit radial anisotropies in their brightness
distributions which may be indicative of dynamical confinement or sculpting of
the disk particles by unseen planetary bodies. STIS follow-on imaging and
spectroscopy are needed to provide further insight into the nature of the disk
particles. With spectra, we will measure the albedo of the disk dust and
search for complex molecules and water ice. With coronagraphic images, we
will investigate the scattering phase function and hence the composition of
the disk dust as well as measure the disk sizes and shapes with high
precision. Such observations are of fundamental importance in establishing
the physical basis for emergent theories of disk evolution and planet-
building.
================================================================================
Proposal Category: GO
Scientific Category: QAL
ID: 8625
Title: The Metallicity of Gas in the Local Universe: Beyond the
Milky Way
PI: David V. Bowen
PI Institution: Princeton Observatory

We wish to obtain STIS spectra of three QSO/AGN which lie behind nearby
galaxies, to measure the metallicity of the interstellar gas at the present
epoch beyond the local group. We aim to provide the first steps in
establishing a low-redshift anchor to the ever burgeoning abundance
measurements of gas at high redshift, to quantify the range of abundances seen
in the galaxies today, and thereby examine whether our galaxy might simply be
metal rich in comparison. Our data will also provide valuable information for
discriminating between competing models of galaxy evolution. The three probes
are the best available for obtaining UV data with sufficient quality to
reliably measure column densities and Doppler parameters; Q1219+047 passes 21
\h\ through the outer H I disk of M61, where there are no sites of current
star formation; Mrk 205 shines through the inter-arm region of NGC 4319, and
can be used to construct the first UV absorption-line atlas of a galaxy beyond
the Magellanic Clouds; and Q1543+489 directly intercepts an intergalactic H I
cloud associated with two nearby galaxies. In this latter case, direct
measurement of the cloud's metallicity and hydrogen column density will also
enable us to constrain the ionization parameter of the UV background radiation
field.
================================================================================
Proposal Category: GO
Scientific Category: QAL
ID: 8626
Title: Spatially Resolved Spectroscopy of APM08279+5255
PI: Sara Ellison
PI Institution: Institute of Astronomy

We propose to obtain spatially resolved, high resolution spectra of the
z=3.911 BAL quasar, APM 08279+5255. This ultra-luminous QSO is a triply
imaged gravitationally lensed system with image separations of 0 nd38 -- 0
nd15. Ground-based observations of this bright source have revealed a rich
absorption spectrum caused by both intervening material and the complex QSO
environment and BAL flows. The proposed STIS spectrum, which will
spatially resolve the individual quasar images, is a unique
opportunity to probe the numerous intervening systems on sub-kpc scales,
providing: o a sensitive probe of the structure of intervening galaxy
halos and metal line systems on scales of ~ 0.2 -- 1.6 kpc h^-1, their
kinematics and spatial extents, o multiple sightlines through the complex
BAL flow on parsec scales, yielding information on ionization, kinematics and
metal enrichment, We also request 5 orbits with WFPC2 in order to detect
and measure the centroid of the lensing galaxy; this will provide the
necessary information to remove the degeneracy in the present gravitational
lensing models.
================================================================================
Proposal Category: GO
Scientific Category: SF
ID: 8627
Title: TESTING THEORIES OF WIND/JET PRODUCTION IN YSOs
PI: Nuria Calvet
PI Institution: Smithsonian Astrophysical Observatory

We propose to use STIS ultraviolet spectroscopy to test theories of jet/wind
production from the accretion disks of low-mass young stellar objects,
providing new insight into disk physics, accretion energy balance, and jet
collimation. STIS observations of the Fe II ultraviolet lines in absorption
will probe lower-density and lower-temperature material than optical forbidden
and permitted emission lines, and thus provide unique information on jet/wind
launching and acceleration. Velocity-resolved spectra will distinguish between
X-wind models, in which all the mass ejection occurs from the inner disk edge,
and disk wind models, where the flow originates from a much larger area of the
disk. Our results will provide important new constraints on the best-studied,
best-understood astrophysical jet systems.
================================================================================
Proposal Category: GO
Scientific Category: SF
ID: 8628
Title: High Density (~ 10^9 cm^-3) gas in the jet formation
region of T Tauri stars
PI: Ana I. Gomez de Castro
PI Institution: Instituto de Astronom'\ia y Geodesia

Outflow is ubiquotous during star formation however the mechanism which drives
it, is still uknown. The key observational information about how outflow is
initiated is contained within a region of angular size smaller than 0.1 arcsec
(for the nearest stars) which is not accessible to direct imaging. It has been
shown that the jet density increases towards the source but the commonly used
optical forbidden lines cannot probe densities higher than ~ 10^6 cm^-3. An
analysis of the ultraviolet tracers of shocked material carried out by us and
based on data from the HST Archive has shown that jet emission is also
detected from the UV semiforbidden lines of C iii and Si iii . The
infered electronic density of the emitting gas is ~ 10^9 - 10^10 cm^-3
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8629
Title: The Search for ``True'' Starburst Dust and the Importance
of Metallicity on Properties of O & B Stars
PI: Fred C. Bruhweiler
PI Institution: The Catholic Univ. of America

Much of what we know about starburst (SB) galaxies, at low and high redshift,
depends upon the nature of the SB dust extinction and the intrinsic physical
parameters of OB stars versus metallicity. Typically SBs, unlike our Galaxy,
exhibit extinction laws with no 2200Angstrom\ peak. There is little
information on the effects of dense star-formation on dust extinction
properties. Specifically, no UV-visual extinction studies exist for the dense
star-forming regions of 30 Dor (LMC) and NGC 346 (SMC), which represent prime
laboratories for studying these effects. These regions have the highest
concentration of young O stars in these galaxies, where 30 Dor is the nearest
example of a definite starburst. Using the 2-D capability of STIS, we will a.)
perform the first UV-visual extinction study of the dense regions of 30 Dor
(in and around R136) and NGC 346, b.) produce unreddened OB star flux
distributions in 30 Dor and NGC 346, c.) use these results to derive effective
temperature, luminosity, and mass-loss rate correlations with spectral type
and metallicity, and d.) explore if the extinction for the cores of 30 Dor
and NGC 346 can be used to generate ``true'' starburst extinction laws.
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8630
Title: The Deepest Far-UV Imaging Survey of Globular Clusters:
NGC 6752 and NGC 6397
PI: Michael Shara
PI Institution: American Museum of Natural History

A few very close binaries can drive the dynamical evolution of an entire
globular cluster. We propose the deepest UV imagery ever obtained on globular
clusters to search for cataclysmic variables (CVs). CVs should be relatively
easy to find in globular cores with HST, but there is a remarkable dearth of
detected CVs in globular clusters relative to the large numbers predicted by
tidal capture theory. This calls into serious doubt all of our understanding
of globular cluster dynamical evolution. If most CVs in globular clusters are
much fainter than canonical classical and dwarf novae, then tidal capture
theory (and our claim to understand cluster evolution) can be salvaged. We
propose to image the globular clusters NGC 6752 and NGC 6397 in the passband
where CVs emit most of their radiation: the far UV, and at Lyalpha. Using the
FUV-MAMA detector on STIS, we will reach an equivalent optical limiting
magnitude of M_V = 13 at S/N=10 which is sensitive enough to detect even the
faintest known CVs. If few or no faint CVs are found, then theorists will have
run out of phase space and simple tidal capture theory will be shown to have
made an incorrect prediction. This would force a major revision in our theory
of tidal capture, and our understanding of globular cluster dynamical
evolution.
================================================================================
Proposal Category: SNAP
Scientific Category: AGN
ID: 8631
Title: Bright Quasar Close Lensing Search II
PI: Michael Gregg
PI Institution: University of California, Davis

enlargethispage0.25in We propose to expand our Cycle 8 second generation HST
snapshot survey of bright quasars, optimized to find lenses with component
image separations < 1". Most models of quasar lensing predict distributions
which peak at separations in the range 0arcs5 to 1", yet the observed
distribution of lenses peaks at 1arcs3. The lack of systems with close
separations is difficult to reconcile with a flat universe, preferred by
theory (inflation) and the observational determinations of the cosmological
constant from type Ia supernovae. Our Cycle 8 survey improves over the
earlier pre-refurbishment snapshot survey of quasars (Bahcall et al.\ 1992;
Maoz et al.\ 1993) in several important respects. With the restored PSF and
the image quality of STIS, the new images are considerably more sensitive to
the presence of both close separation and faint lens components. Our
snapshots are guided, multiple exposure observations, allowing a much better
final data product. We are also obtaining exposures in both Clear and
LongPass modes, providing immediate color information to gauge the chances
that a pair of close images is consistent with lensing. At the time of this
writing, about 80 of our 300 allocated snapshots have been taken. The early
returns are exciting: we have one small (0arcs6) separation lens, plus 3
additional lens candidates at larger separations. Encouraged by these
results, we propose to expand the survey in Cycle 9.
================================================================================
Proposal Category: SNAP
Scientific Category: GAL
ID: 8632
Title: A UV Atlas of Nearby Galaxies
PI: Mauro Giavalisco
PI Institution: Space Telescope Science Institute

We propose a snapshot survey of local galaxies at UV wavelengths with WFPC2
and the F300W filter. The aim of the project is to build a reference UV Atlas
of normal galaxies, whose optical images are well known, with the highest
possible degree of information, covering all the morphological types and
luminosity classes. The F300W passband is significantly bluer than the Johnson
U, its transmittance is not limited by the atmosphere, and it offers adequate
throughput for this project. The sample is extracted from the Revised Shapley-
Ames Catalog and includes 130 galaxies with a redshift distribution centered
around ~ 1500 km/sec and FWHM~ 500 km/s. At these redshifts the field-of-view
of WFPC2 covers ~ 23 kpc, or approximately the Holmberg diameter of a large
spiral galaxy. No systematic imaging of local galaxies at wavelengths bluer
than the B band are currently available and the general properties of the
various Hubble types in the UV are essentially unknown. Still, this
information is crucial for a variety of studies, which include star-formation
activity and evolution, nuclear activity, the physics of the ISM, the
evolution of galaxy morphology. The WFPC2 UV Atlas will provide a unique
reference data set which will be valuable for a wide variety of future
observations, both ground--based and with HST. This project is a service to
the community, and we waive the proprietary period.
================================================================================
Proposal Category: SNAP
Scientific Category: HS
ID: 8633
Title: The Physical Parameters of the Hottest, Most Luminous
Stars as a Function of Metallicity
PI: Philip Massey
PI Institution: National Optical Astronomy Observatories

We have obtained excellent, new ground-based blue optical and HAlpha spectra
of a sample of very early-type stars in the Magellanic Clouds in order to
measure their physical properties, and compare these to the extensive data
that exists for higher metallicity Galactic stars. What we lack is knowledge
of the stellar wind terminal velocities for our stars, necessary to constrain
the stellar models. These can only be measured with STIS/FUV on HST. In
addition, we will obtain higher spatial resolution data on the HAlpha line for
six of our stars for which nebular contamination is significant even with long
-slit subtraction in out ground-based data. These new HST data will allow us
to understand how the spectral type to effective temperatures depend upon
metallicity (necessary in determining IMFs), as well as allow us to explore
the astrophysically interesting regime of stars of extreme temperatures,
masses and luminosities. Together with the optical data, they will also
provide important information about the strengths of stellar winds at extreme
luminosities and the calibration of the Wind Momentum - Luminosity
Relationship at lower metallicities.
================================================================================
Proposal Category: SNAP
Scientific Category: SS
ID: 8634
Title: Atmospheric Variability on Uranus and Neptune
PI: Kathy Rages
PI Institution: Space Physics Research Institute/NASA Ames Research Center

We propose snapshot observations of Uranus and Neptune to monitor changes in
their atmospheres on time scales of months to years. Uranus is rapidly
approaching equinox in 2007, with another 4degrees\ of latitude in the
northern hemisphere becoming visible every year. Recent HST images during
this unique epoch (6818: Hammel, Lockwood, and Rages; 7429: Tomasko and
Karkoschka; 7885: Hammel, Karkoschka, and Marley) have revealed: (i) strongly
wavelength-dependent latitudinal structure, (ii) the presence of numerous
visible-wavelength cloud features in the northern hemisphere, and, (iii) in
the near-IR, discrete features northward of 25degrees N that have the highest
contrast ever seen for a Uranian cloud (Karkoschka 1998c; Hammel et al.\
1999). Long-term ground- based observations (Lockwood and Thompson 1999) show
seasonal brightness changes whose origins are not well understood. Recent IR
images of Neptune
(http://www2.keck.hawaii.edu:3636/realpublic/ao/neptune.html) obtained using
adaptive optics on the Keck Telescope indicate that a new ``Bright Companion"
type of feature has recently appeared in the southern hemisphere. Snapshot
observations of these two dynamic planets can supply context in which to
discern the nature of long-term changes in their latitudinal atmospheric bands
and to track the appearance, movement, and disappearance of discrete albedo
features.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8635
Title: A test of pulsation and diffusion theory for subluminous
B stars
PI: Ulrich Heber
PI Institution: Dr. Remeis-Sternwarte

The recent discovery of radial and nonradial mode pulsations in nearly 20 sdB
stars makes it possible to use asteroseismology to probe the internal
structure of these stars and discern their evolutionary status; this is needed
for reasons as diverse as understanding the late stages of stellar evolution
and the calibration of the observed ultraviolet upturn in giant elliptical
galaxies as an age indicator. Central to any asteroseismological study is an
identification of the pulsation driving mechanism; evidence to date suggests
that this is due to the recently discovered heavy metal opacity. The
necessary metal abundance has to be maintained by diffusive equilibrium
between gravitational settling and radiative levitation. Abundance analyses of
high resolution optical spectra have, however, revealed that the surface iron
abundance is not discriminating between pulsating and non-pulsating sdB stars.
We propose to extend the abundance analyses of three pulsating sdB stars and
two non-pulsating sdB stars to chemical elements unobservable from the ground
using echelle UV spectra; this would enable diffusion/pulsation calculations
to be tested by searching for significant differences in their surface
abundance patterns. The targets are chosen to cover the full range of sdB
gravities since \logg\ is the dominant parameter for both diffusion and
pulsation.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8636
Title: Metal abundances in very hot DA white dwarfs -- a test of
diffusion theory
PI: Ralf Napiwotzki
PI Institution: Dr. Remeis-Sternwarte

The photospheric abundances of white dwarfs are controlled by diffusion
processes like gravitational settling and radiative levitation. UV, EUV and X-
ray observations revealed a large metallicity spread from star to star, which
cannot be explained by state-of-the-art stationary diffusion calculations.
Additional processes, e.g. a weak stellar wind, have been invoked. A
contrasting pair of extremely hot DA white dwarfs, recently discovered by the
HS survey, has very similar temperature and gravity, but probably very
different metal abundances. HS 0505+0112 is unique because it is the only H-
rich hot white dwarf known to show optical C lines. Balmer line fitting yields
further evidence that the heavy element abundances of HS0505+0112 must be
high. In contrast HS 0615+6535 displays Balmer lines only and fitting their
line profiles is consistent with an unusually low amount of metals. We
propose to determine abundances of C,N,O,Si and Fe and Ni directly from STIS
UV spectra by means of fully metal line blanketed NLTE model atmospheres.
Indications of mass loss will also be searched for providing us with an
important check of the diffusion theory in white dwarfs. Both stars are
also ideally suited for a test, whether the C, N, O line opacity can account
for the Balmer line discrepancy noted for the analysis of very hot H-rich
stars.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8637
Title: Distance to the prototype WD showing signatures of a
super-hot wind
PI: Klaus Werner
PI Institution: Universitaet Tuebingen, Institut fuer Astronomie und
Astrophysik

We propose to determine the distance to the prototype of a new class of hot
white dwarfs (WD). Their optical spectra reveal absorption lines from ultra-
high ionized metals (e.g.\ IonOVIII), a phenomenon never observed before in
any astronomical object. The occurrence of such features requires temperatures
in the order of 10^6 K, far in excess of the stellar T_ eff. The asymmetric
line profiles suggest formation in a rapidly accelerating high-speed wind
(10,000 km s^-1). These stars represent the most convincing proof for on-going
mass-loss from WDs. We have demonstrated that a large fraction of hot WDs
shows this phenomenon, concluding that perhaps all WD go through this
evolutionary stage. For the prototype we will determine stellar parameters and
possible consequences of the mass-loss for WD evolution on hand of detailed
NLTE modeling. The distance to the star is an essential prerequisite for this.
We propose to derive the distance spectroscopically by determination of
spectral type and luminosity class of the cool companion of the WD.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8638
Title: Temperature scale and metal abundances of hot hydrogen-
rich central stars of planetary nebulae
PI: Klaus Werner
PI Institution: Universitaet Tuebingen, Institut fuer Astronomie und
Astrophysik

We propose UV spectroscopy of a sample of hot hydrogen-rich central stars of
PNe, covering the hottest phase of post-AGB evolution (T_ eff>70 000 K). The
spectra shall be analyzed with fully metal line blanketed NLTE model
atmospheres in order to determine T_ eff, surface gravity, and chemical
composition. The results will address the following problems: 1. The
temperature scale of the hottest central stars is poorly known. Iron lines,
only accessible in the UV, are ideal temperature indicators to set up a
reliable temperature scale. 2. Depending on the particular star, the derived
metal abundances are either dominated by current diffusion processes or they
originate from dredge-up phases during previous AGB evolution. We expect that
our sample comprises different objects so that both processes/phases can be
studied in detail. 2a. Those objects, which show qualitatively a metal
abundance pattern which points at dredge-up phases, can be used to
quantitatively check against abundance predictions of stellar evolution
theory. 2b. The other objects, where gravitational diffusion and radiative
acceleration determine the photospheric metal abundances, will be used to
check our NLTE models which for the first time include diffusion processes
self-consistently.
================================================================================
Proposal Category: GO
Scientific Category: AGN
ID: 8639
Title: The Origin of Gaseous Outflows in Active Galaxies
PI: Andrew Wilson
PI Institution: University of Maryland

We have recently obtained HST PC images of the ionized gas in the Circinus
galaxy, a nearby (distance 4 Mpc) Seyfert 2. The images reveal that the
nuclear (i.e. the inner 2^ = 40 pc) high excitation gas is ``V-shaped'' and
represents the inner part of the ``ionization cone'' seen previously on much
larger scales in ground-based observations. At 10 - 15^ = 190 - 280 pc from
the nucleus, there is an elliptical ring of high excitation gas, which we
infer to be the end of the intrinsically circular cone viewed at its known
orientation. The images thus suggest that the observed emission lies along the
boundary of a conical structure, a situation which has probably originated
through mass entrainment of dense gas in the galaxy disk along the edges of a
low density outflow. We wish to obtain long slit observations of this
structure. Our goals are: 1) to confirm or reject this picture kinematically;
2) investigate how gas is entrained into the outflow from the dense ism in the
galaxy disk in the inner (< 40 pc) region of the outflow at unprecedented
spatial resolution for a Seyfert galaxy (our resolution of 1 pc is comparable
to or smaller than the expected radius of the inner edge of the putative
blocking ``torus''); 3) distinguish between collimation of ionization photons
or of gaseous outflow as the origin of the ``ionization cone''; 4) attempt to
measure the mass of the nuclear black hole using a long slit spectrum of the
disk HII regions.
================================================================================
Proposal Category: GO
Scientific Category: COS
ID: 8640
Title: A Public STIS Survey of the Host Galaxies of Gamma-Ray
Bursts
PI: Stephen Holland
PI Institution: University of Aarhus

We propose to obtain high-resolution STIS images of the fields containing
every gamma-ray burst with well-localized coordinates; i.e.\ the burst has
been localized to within ~ 1". The goal of this survey is to obtain a uniform
sample of images of the host galaxies of these bursts. This data will be used
to search for host galaxies that are too faint to be discovered by ground-
based searches, to study the morphology of host galaxies, and to compare the
population of galaxies that contain gamma-ray bursts to other populations of
galaxies such as Lyman Break Galaxies, Damped Lyman-Alpha Absorption Systems,
infrared galaxies. This survey will allow us to probe the star-formation rate
in the high-redshift Universe and study the nature of stellar populations at
early epochs. We intend to waive all proprietary rights to this data, and will
make optimally-combined images available to the astronomical community as soon
as they are produced.
================================================================================
Proposal Category: GO
Scientific Category: COS
ID: 8641
Title: Testing the Accelerating Universe
PI: Brian Schmidt
PI Institution: Mt.Stromlo & Siding Spring Observatories

Type Ia supernovae provide evidence for an accelerating universe: an
extraordinary result that needs to be rigorously tested. The two chief
alternatives to a cosmological source for the observed shape of the high-z
Hubble diagram (z >= 0.4) are dust that absorbs, but does not redden much, and
intrinsic changes in the luminosity of distant supernovae due to the age of
the stellar population or the chemical composition of the progenitor stars.
We propose to test the generic predictions of composition models and the
specific predictions of dust models through very wide wavelength coverage
UBVRI observations of 7 supernovae near z = 0.5. These observations, with
precise restframe UBVR from HST and restframe I from large groundbased
telescopes, will provide enough information for a definitive test of the
``grey'' dust proposal, while they also place the most stringent constraints
on differences that could be attributed to chemical differences or age
differences between nearby and distant samples of SN Ia. The unique restframe
U-band observations proposed here will be especially important in comparing SN
Ia at z=0, where we have a sample, and z=0.5, where we don't, and in
interpreting the data from very high redshift supernovae with z>=1. Our goal
is cosmology, our measuring tool is supernovae, and we need precise, wide
wavelength measurements at z=0.5 to test the quality of this yardstick.
================================================================================
Proposal Category: GO
Scientific Category: COS
ID: 8642
Title: Deep Imaging of the Probable Einstein Ring 1517+656
PI: Meg Urry
PI Institution: Space Telescope Science Institute

A short WFPC2 F702W snapshot image of the BL Lac object 1517+656 has revealed
three surrounding arcs, subsequently confirmed by a longer NOT observation,
making this a probable new Einstein ring. Deeper high-resolution imaging is
required to determine unambiguously the nature of this intriguing source. We
propose to obtain a deep STIS/CCD + F28X50LP image to map the detailed
structure of the arcs, and WFPC2 F555W and F814W images to measure their
colors. The STIS data will have the depth and resolution required for
iterative back-mapping of the arcs, providing a unique determination of the
mass distribution of the lens. The extreme narrowness of the arcs makes ground
-based observations useless for this purpose. Combined with the WFPC2 data, we
will have sufficient color information to constrain the photometric redshift
and stellar population of each arc (impossible with the ground-based data
because of the instability of the required deconvolution), as well as of other
galaxies detected in the field.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8643
Title: Ultraviolet Properties of the Metal Rich M87 Globular
Cluster System
PI: Robert O'Connell
PI Institution: University of Virginia

We propose to use STIS imaging to obtain far-ultraviolet photometry of the
metal rich globular cluster system of the elliptical galaxy M87. This system
represents a key link between the well understood populations of the clusters
and the hot stars in elliptical galaxies, where our physical insight is
presently limited. Our goal is to establish the relationship between cluster
metal abundance and the production of UV-bright populations of stars on the
``extreme horizontal branch'' at T(eff) > 16000K. These stars are the source
of the surprising ``ultraviolet-upturn'' phenomenon in elliptical galaxies.
Our observations will fill a major gap in the present coverage of cluster
metal abundances. This would be an important step in understanding the
dependence of the upturn on its parent stellar population. A basic motivation
is the expectation that the UV-upturn could be the most sensitive probe of the
ages and abundances of elliptical galaxy populations. We plan to observe 3
fields in M87, which will provide a sample of ~ 30--50 UV-detected objects in
the brightest 3 magnitudes of its cluster luminosity function. The program is
technically challenging but appears feasible. Relatively long integrations
are needed, under conditions of minimum dayglow emission from Earth's
atmosphere.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8644
Title: Galaxy Recycling in Clusters
PI: Michael West
PI Institution: University of Hawaii

We propose to obtain deep WFPC2 B, V, and I images of two unusual, extended,
low surface brightness plumes of material recently discovered in the Coma and
Centaurus clusters. These plumes are most likely transient tidal debris
resulting from the destruction of galaxies as they passed through the cores of
these clusters. Over time, this debris will spread throughout the cluster
potential, augmenting the intergalactic populations of stars, globular
clusters, dwarf galaxies, and gas. Some of this material may also be
incorporated into the halos of the central dominant galaxies. In these plumes
we are witnessing the ongoing formation of the diffuse intracluster background
of stellar light seen in many rich clusters, as well as the material from
which cD galaxies themselves may be built. This is recycling on a cosmic
scale. Determining the nature of this recycled material is key to
understanding the formation and evolution of the intergalactic stellar
population, as well as the evolution of the galaxy populations in clusters.
HST images of these two plumes will enable direct study of their stellar
populations, specifically, the number of bright supergiants, globular
clusters, and star forming regions which may be present.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8645
Title: A Survey of Mid-UV Morphology of Nearby Galaxies: Galaxy
Structure and Faint Galaxy Evolution
PI: Rogier Windhorst
PI Institution: Arizona State Univ., Physics & Astronomy

\n Too little is known about the relation between star formation and the
global physical characteristics of galaxies to interpret the morphologies of
distant galaxies in terms of their evolutionary status. Faint galaxies are
primarily observed by HST in their restframe mid-ultraviolet. They resemble
nearby late-type galaxies, but are they really physically similar classes of
objects? We propose to address this question through a WFPC2 imaging survey of
37 nearby galaxies in two mid-UV bands. Our sample is carefully selected for
size and surface brightness and has a large amount of correlative data
available. A wide range of Hubble types and inclinations is included, with
emphasis on late-types/irregulars/peculiars. All objects have ground-based
UBVRIJHK, and 15 have far-UV UIT images. The mid-UV is the missing keystone.
Our proposed data set will be unique, can be applied to a wide range of
problems, and will be made public immediately. Our goals are: 1.
Consistently classify polychromatic structures and photometric properties of
galaxies from 0.15-2.2 mu. 2. Map the spatial distribution, luminosities, and
sizes of star-forming regions responsible for the UV morphology, and relate
these to global galaxy properties. 3. Provide local benchmark images that we
can redshift to z~1-->3 for quantitative comparison to the morphological and
photometric properties of high redshift galaxies.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8646
Title: Observing the next nearby supernova
PI: John Bahcall
PI Institution: Institute for Advanced Study

If a neutrino-producing supernova (SN) explodes in the Galaxy, the Large or
Small Magellanic Clouds, or a close member of the Local Group, it will be
detected first by operating neutrino experiments: Super-Kamiokande, SNO,
MACRO, and AMANDA. The supernova neutrino early warning system will notify
photon observers throughout the world within an hour of the neutrino
detection. Although the per-year probability of observing a neutrino SN
(within 100 kpc) is small, the detection would be importantly scientifically
and of widespread interest. The optical counterpart could be much brighter
than normal extragalactic SNe. A bright nearby supernova detected by other
means would also be of great interest and should activate this proposal. We
propose unique STIS ultraviolet spectroscopic observations to measure the
principal metallic lines, and hence the composition, velocity, and physical
state, of the outermost atmosphere of the exploded star. In addition, we
propose narrow- and broad-band imaging to provide information about the
stellar environment and early morphology unobtainable from the ground. The
data, especially images, will be valuable for public outreach and will be
released immediately by NASA.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8647
Title: HST/RXTE Observations of SXTs: Black Hole Accretion
Outbursts
PI: Carole Haswell
PI Institution: Open University

UV observations of soft X-ray transients (SXTs) will be made using STIS. This
is part of an extensive multiwavelength target of opportunity campaign to
monitor newly discovered SXTs in outburst and throughout the subsequent
decline. A high proportion of SXTs harbor black holes, so these observations
provide an unrivalled opportunity to obtain high quality data from an
accreting black hole. UV data is a keystone of our multiwavelength campaign
because the disk regions of interest radiate predominantly in the UV. Emission
lines will allow us to probe the kinematics of the inner disk region.
Multiwavelength observations will probe the physics of the accretion flow
throughout the outburst. We will examine the relative strengths of the
reprocessed X-ray flux emitted in the UV, and the UV flux generated by viscous
heating in the accretion flow. The observations will yield detailed
quantitative tests of the models for SXT outbursts. The STIS/MAMA capability
to perform UV spectroscopy with 125 microsecond time resolution will be
exploited with a proven HST/RXTE echo-mapping experiment. This will measure
the size of the reprocessing regions in the accretion disk, and thus probe
morphology changes as the decline proceeds. It is unknown what rapid UV
variability we may find; recent RXTE discoveries suggest this may prove a rich
source of information on the dynamics close to the event horizon.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8648
Title: SINS: The Supernova INtensive Study--Cycle 9
PI: Robert Kirshner
PI Institution: Harvard College Observatory

Supernovae explode to create the chemical history of the Universe and energize
the interstellar gas. They now occupy center stage for the extragalactic
distance scale and cosmology. The SINS program has shown how HST can make
unique contributions to understanding supernovae. HST is better than ever for
this work: STIS is ideal for spatially-resolved observations of SN 1987A,
where a rapidly developing encounter between the fast-moving debris and the
stationary inner ring is underway. Observations of UV emission inside the
inner ring of SN 1987A reveal the location and velocity of the reverse shock
that also produces X-ray and radio emission. We also plan intensive study of
illuminating objects beyond SN 1987A: a Target-of-Opportunity observation of a
bright, new supernova that is certain to be discovered during Cycle 9, and the
late-time observations of SN 1999by (SN Ia) and SN 1998bw, (SN Ic? and
probably Gamma-ray burst). We request a 24-hour turn-around because the UV
flux from supernovae changes rapidly in the first days and reveals much about
the star. We will explore the UV emission from supernovae, exploit the spatial
resolution of HST, and press the late-time observations of supernovae into
uncharted territory. The SINS team enriches HST data with extensive ground-
based support and analytic power to help understand the final and most violent
stage of stellar evolution.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8649
Title: Probing Stellar Interiors Via Convective Dredge-up in DQ
White Dwarfs
PI: Judith Provencal
PI Institution: University of Delaware

The composition and structure of white dwarf stars contain a wealth of
information about processes occurring in contemporary main sequence stars like
our sun. We use this information to build theoretical models placing limits
on the star formation history and age of the Galactic disk. One of the largest
uncertainties in our models is the unknown core composition of a white dwarf.
We generally assume a mixture of carbon and oxygen, but the exact ratio is
unknown. This uncertainty introduces a 20\ dwarfs offer our only opportunity
to directly observe the actual carbon/oxygen ratio in a white dwarf core. DQs
are are otherwise normal helium-rich stars displaying carbon features in their
spectra. The observed carbon in these objects results from dredge-up of the
underlying core by the helium convection zone. Recent theoretical work argues
that oxygen should also be present in detectable amounts in the more massive
DQ stars. We propose a modest investment of HST time to determine for the
first time whether a white dwarf core contains a substantial quantity of
oxygen. We will search for trace amounts of oxygen in the atmosphere of a
massive DQ as an important step towards resolving this question.
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8650
Title: The Interplanetary Medium Hydrogen Velocity Distribution
PI: John T. Clarke
PI Institution: University of Michigan

Neutral atoms from the interstellar medium (ISM) flow into the solar system
producing a diffuse emission at 1216 Angstrom by resonant scattering of solar
H Ly-alpha emission. This wind contains the velocity distribution of the
local ISM, plus modifications by solar gravity, radiation pressure, and
ionization near the Sun, and the Ly-alpha emission line profile reveals these
velocity signatures. Compared with the He flow at 26kms, consistent with the
local ISM cloud, the H velocity of 18-21kms suggests an additional alteration
of the H atom velocity distribution by charge exchange at the heliospheric
interface. In cycles 1 and 4 we obtained initial GHRS echelle A Ly-alpha line
profiles in 3 look directions. For cycle 9 we propose three focussed
observations, taking higher sensitivity STIS echelle spectra to address the
following key questions about the interplanetary H: 1) we will accurately
measure the ratio of solar gravity to radiation pressure on the flow, 2) we
will obtain upwind spectra close in time to FUSE spectra of the optically thin
Ly-beta emission to directly measure the optical depth, and 3) we will obtain
high S/N line profiles upwind to determine the extent of slowing of the inflow
velocity distribution indicated in earlier HST and SOHO observations. The end
goals of this program are to characterize the properties of the local ISM and
its modification at the heliospheric interface.
================================================================================
Proposal Category: GO
Scientific Category: QAL
ID: 8651
Title: STIS UV Spectroscopy in the Magellanic Bridge: A Typical
QSO Absorption Line System?
PI: Chip Kobulnicky
PI Institution: University of Wisconsin-Madison

We are proposing STIS echelle UV absorption line spectroscopy through the
Magellanic Bridge (near the SMC) to probe the temperature, ionization, and
kinematic structure in a metal-poor environment like those observed in the
early universe. The sightline toward the QSO B0312-770 is especially
interesting because of the proximity of the absorber (~ 60 kpc) and the radio
loud background source. Using 21-cm absorption and emission spectroscopy we
have measured H I column densities of 10^20 cm^-2 which approach those in
damped LyAlpha systems. Most importantly, we measure well-constrained spin
temperatures for the absorbing neutral hydrogen components, T_S=30-200 K. By
comparing the velocity structure and optical depths of common UV lines like Mg
I, Mg II, Si II, Si IV, C IV, with the 21-cm diagnostics, we will identify the
mixture of physical phases (hot and cold) and kinematic structure that
comprise a nearby metal-poor environment for comparison to the high-z
universe. If this sightline resembles the high-z UV absorbers, then the
existence of ongoing star formation in the Magellanic Bridge implies that QSOs
absorption line systems may be active sites of star formation as well.
================================================================================
Proposal Category: GO
Scientific Category: QAL
ID: 8652
Title: Evolution of the Extinction Curve
PI: Alain Smette
PI Institution: NASA/Goddard Space Flight Center

The extinction curve has been determined precisely in only a few galaxies: the
Milky Way (MW), the Large and Small Magellanic clouds (LMC and SMC). It has
also been determined towards several starburst galaxies, but its significance
then depends on the precise star-gas-dust geometry. There is no general
agreement on a model to explain its characteristics; laboratory experiments
fail to reproduce the famous 2175Angstrom feature under the conditions of the
popular silicate-graphite model. The MW, LMC and SMC extinction curves are
generally used to bracket extinction curves in other galaxies. Extinction by
dust influences the determination of the Hubble constant from cepheids, of
Omega_\mathrm M and Lambda using Type Ia Supernovae or gravitational lenses,
of the cosmological density of gas and star formation history and the origin
the Cosmic Infrared Background. A larger sample of extinction curves is thus
urgently needed. Recently, Jean & Surdej (1998) described a method to recover
the extinction curve based on high signal-to-noise, low-resolution spectra of
the multiple images of gravitationally lensed quasars. We propose to apply
this method to 3 quadruply imaged quasars in order to recover the extinction
curve of galaxies sampling the redshift range 0.04 to measure the HI column density along each line-of-sight in order to estimate
their gas-to-dust ratio.
================================================================================
Proposal Category: GO
Scientific Category: SF
ID: 8653
Title: Collimation and Physical Conditions Within the HH 30
Protostellar Jet
PI: Patrick Hartigan
PI Institution: Rice University

We propose to observe the protostellar jet HH 30 through a wide slit with STIS
in order to determine the distance from the star that the jet becomes
collimated, and to diagnose the density, temperature, shock structure, and
ionization within the collimation region. The proposed observations will
provide an image of the jet in each emission line across the entire optical
spectrum with minimal contamination from the reflection nebula near the star,
a marked improvement over existing narrowband images that cover only a few
lines which emit over a limited range of densities and ionization states.
Ratios of the new emission-line images will probe the physical conditions in
the jet with HST spatial resolution and make it possible to observe the shape
and location of any shocks in the flow, resolve the cooling layers behind
these shocks, and trace the recombination of any ionized gas that emerges from
the base of the jet. The proximity and brightness of HH 30 together with its
favorable inclination angle make this an ideal object to study jet
collimation. The new STIS spectra are precisely what are needed to test MHD
models of jet collimation from accretion disks. Understanding how jets
originate, become collimated, and form shocks has profound implications for
the distribution of magnetic fields and angular momentum within accretion
disks, which in turn control how stars and planets form.
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8654
Title: Confirmation of Black Hole, Planetary, and Binary
Microlensing Events
PI: David Bennett
PI Institution: University of Notre Dame

We propose WFPC2 images of five MACHO Project microlensing events in order to
confirm our microlensing models which indicate that these events were caused
by black holes and stars with extra-solar planets. Our microlensing parallax
fits for MACHO-96-BLG-5 and MACHO-97-BLG-6 indicate that the lenses are likely
to be black holes of ~ 40M(sun) and ~ 8M(sun), respectively, and we can test
these models by comparing the amount of stellar blended predicted by the model
with the blended determined from the WFPC2 images. For the large mass black
hole candidate MACHO-96-BLG-5, we propose a time series of observations to
follow the declining magnification of ~ 0.4 mag over the next several years as
predicted by the microlensing model. For the two extra-solar planet candidates
reported by the Microlensing Planet Search (MPS) Collaboration, MACHO-97-BLG-
41 and MACHO-98-BLG-35, we propose to test the planetary microlensing models
by determining the amount of blending between each source star and its
neighbors. Our observations of MACHO-97-BLG-41, will serve as a first epoch
for the possible observation of this triple lens system moving away from the
source star. Finally, we propose to image binary lensing event MACHO-98-SMC-1
to test our ability to determine the location of the lens systems for such
events.
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8655
Title: Geometric Distances of Globular Clusters (GO part)
PI: Ivan King
PI Institution: University of California, Berkeley

This is a proposal to establish a globular-cluster distance scale of
unprecedented accuracy and reliability, with far-reaching impact on the
distance and time scales of cosmology. Our method is to compare internal
dispersions of proper motion with ground-based determinations of the
dispersion of radial velocities. The prospect is a geometrically based
distance scale with an accuracy of better than 2\ ability to make such
measurements, and we are progressing with the conversion of them to a distance
for the cluster. Our project has two parts: (1) Where possible, we use
archival observations for both astrometric epochs (see accompanying AR
proposal, which covers 2 clusters). (2) The present proposal covers 5 more
clusters for which an archival first epoch exists but for which we lack second
-epoch observations. With this proposal, the accompanying AR proposal, and
other HST collaborations in which we are involved, we expect to determine
accurate distances for 13 clusters, with a large range of metallicities and
second-parameter characteristics. (Moreover, we intend to cover additional
clusters in future ACS proposals.)
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8656
Title: The Hydrogen-Burning Limit in the Globular Cluster NGC
6397 (GO part)
PI: Ivan King
PI Institution: University of California, Berkeley

We propose a major enhancement of an earlier study of the bottom of the main
sequence of NGC 6397, the globular cluster with the smallest distance modulus.
In earlier work the lowest part of the MS had been lost among the numerically
dominant field stars; but accurate astrometry, over a baseline of a few years,
now allows an excellent proper-motion separation of faint cluster stars from
the field. The purified CMD follows the main sequence to its ``end" (i.e.,
the terminal plunge of the LF). Just as the MS CMD gives a mass--radius
relation, we show in a new way how this LF can give a mass--luminosity
relation; both of these offer unique checks on theory. Our single WFPC2
field, however, had only a small number of stars in this range, too few to set
firm restraints on the theories. We propose now to increase the number of
such stars by a large factor by (1) getting 2nd-epoch images for three more
fields in the cluster and (2), in an accompanying AR proposal, remeasuring our
previous images, and others that exist, to the deeper limit that we know can
be attained. The number and the magnitudes of these faintest stars will
greatly strengthen the constraints that we place on structure and atmosphere
theories of lower-main-sequence stars. In each field we will also measure the
anisotropy of internal stellar motions, which is predicted to be large in a
collapsed-core cluster such as this one.
================================================================================
Proposal Category: GO
Scientific Category: SS
ID: 8657
Title: Jovian Auroral Variability Due to the Solar
Wind/Magnetosphere Interaction
PI: John T. Clarke
PI Institution: University of Michigan

instrumentSTIS HST/STIS observations of Jupiter's aurora have revealed many
fascinating and detailed aspects of these complex and energetic emission
processes. The main UV emissions and their morphologies have been determined,
with different emissions varying on time scales from seconds to days. With
observations spaced months apart, and no record of the solar wind conditions
near Jupiter, however, it has not been possible to determine the cause and
effect relations governing the many variations. A unique opportunity to study
these complex variations will exist when the Cassini spacecraft flys by
Jupiter in December 2000. We propose to perform STIS observations of
Jupiter's UV aurora in two campaigns along with Cassini measurements of the
solar wind before closest approach, then another campaign when Cassini is just
past Jupiter and looking back at the night side aurora. The proposed series
of STIS observations, covering nearly complete Jupiter rotations, will permit
us to perform several known key measurements of the auroral emissions, and
also to study uniquely the effects of solar wind variations on the auroral
morphology.
================================================================================
Proposal Category: GO
Scientific Category: SS
ID: 8658
Title: Atmospheric Escape and the D/H Ratio in Mars' Atmosphere
PI: John T. Clarke
PI Institution: University of Michigan

The highly extended upper atmosphere and the UV airglow of Mars have not been
studied by any in situ spacecraft since Mariner 9 in 1972. At the same time,
one of the main elements of NASA's space science program today is the study of
Mars and how it has evolved over time to a hostile environment, compared with
the favorable conditions on the Earth. The availability of long aperture
spatially resolved UV spectra with STIS makes it possible to obtain unique
information on the extended upper atmosphere of Mars by mapping the H and O
dayglow emissions with altitude above the limb. We propose to make these
observations just before Mars opposition near the end of HST cycle 9. Initial
modeling indicates that we will have sufficient angular resolution and
sensitivity to measure the scale heights of the suprathermal atom populations
of H and O atoms. We also propose to determine accurate values for the D and
H columns, and the D/H ratio, in the upper atmosphere of Mars. The present-
day D/H ratio gives vital information leading to understanding the evolution
of Mars' atmosphere, the historic escape of water into space, and potentially
the remaining water abundance on Mars.
================================================================================
Proposal Category: GO
Scientific Category: SS
ID: 8659
Title: High Resolution Spectrum of the Venus Lyman-Alpha Line
Profile
PI: William Colwell
PI Institution: Southwest Research Institute

We propose to record a single high spectral resolution observation of the
Venus Ly-alpha\ line, while HST is within Earth shadow and Venus is at
47.1^degrees solar elongation, with a supporting observation of the Ly-alpha\
geocorona outside the exclusion zone (50^degrees). This Ly-alpha\ line profile
will be compared with emergent line profiles from Venus thermosphere radiative
transfer models to assess the energetics and contributions from supra-thermal
sources of hydrogen, a long-standing issue in Venus aeronomy. This information
will enhance understanding of the pathways of hydrogen escape from Venus and
constrain models of Venus climate evolution. The line profile will be used to
assess the abundance of deuterium in the Venus atmosphere, a quantity with
great importance to atmospheric evolution models. The HST STIS instrument
is the only instrument capable of making these far UV observations with
sufficient spectral resolution to address the details of hydrogen energetics
in the Venus thermosphere and exosphere. HST previously observed Venus with
Esposito as PI (P4518 and P5783).
================================================================================
Proposal Category: GO
Scientific Category: SS
ID: 8660
Title: Saturn's Rings and Small Moons
PI: Richard French
PI Institution: Wellesley College

We propose to continue our long-term survey of Saturn's rings, using the
unique capabilities of the WFPC2, to obtain a coherent set of high resolution,
multi-color images of the Saturnian ring system over the full range of ring
tilt and phase angles accessible from the Earth over the course of 1/4 Saturn
year (7 Earth years). Our Cycle 6 (program 6806) and long-term Cycle 7 (7427)
and Cycle 8 (8398) observations explored the rings from their nearly edge-on
aspect, just after the most recent ring plane crossings, to their current
moderate inclination. Here, we propose to complete our survey during the next
three Saturn oppositions (Cycles 9--11), as the rings gradually approach their
most open configuration, shortly before the arrival of the Cassini spacecraft
at Saturn. Our key goals are to investigate the composition, structure, and
particle properties of the rings from variations of ring brightness and color
with radius, tilt and phase angle, to measure the azimuthal asymmetry of the A
ring and the temporal variability of the clumpy F ring, to follow the
enigmatic behavior of the renegade satellites Prometheus and Pandora, and to
observe the co-orbital satellites Janus and Epimetheus as they exchange orbits
in February 2002.
================================================================================
Proposal Category: GO
Scientific Category: SS
ID: 8661
Title: UV Spectroscopy of the Giant Planet Atmospheres with STIS
PI: Roger Yelle
PI Institution: Northern Arizona University

We propose STIS observations of the atmospheres of Jupiter, Saturn, Uranus,
and Neptune in the ~1600-3100 Angstrom\ spectral region. Analysis of these
observations will be used to determine the abundance and altitude profiles of
gaseous absorbers and aerosols from the millibar region to hundreds of
millibars. We will also determine the H_2 ortho/para ratio. Atmospheric
properties will be derived through comparison of the observations to synthetic
spectra based on model atmospheres and state-of-the-art radiative transfer
calculations, that include raman scattering in a rigorous manner. Results
from this analysis will be used to investigate photochemical processes in the
giant planet atmospheres and to constrain the state of the interiors and the
transport rate between the deep interior and visible atmosphere.
================================================================================
Proposal Category: SNAP
Scientific Category: ISM
ID: 8662
Title: A SNAPSHOT Survey of the Hot Interstellar Medium
PI: James Lauroesch
PI Institution: Northwestern University

We propose to obtain SNAPSHOT STIS echelle observations of key tracers of hot
interstellar gas (ionC4, ionN5, and ionSi4) for selected FUSE Team ionO6
survey targets with known UV fluxes. By taking advantage of the SNAPSHOT
observing mode we will efficiently obtain a large number of spectra suitable
for the study of the highly ionized hot component of the interstellar medium
(ISM). Our goals are to explore the physical conditions in and distribution of
such gas, as well as to explore the nature of the interfaces between the hot
ISM and the other interstellar gas phases. Using inter--comparisons of the
various ionic ratios for ionC4, ionN5, ionO6, and ionSi4, we will be able to
discriminate between the various models for the production of the highly
ionized gas in the Galactic ISM. The survey will also enable detailed studies
of regions already known to contain hot gas through X-ray emission
measurements (e.g., SNRs and radio loops). Currently there are only 14 stars
in the FUSE Team ionO6 survey that have planned or archived HST exposures
that cover the lines of ionC4, ionN5, and ionSi4. We estimate that the
proposed SNAPSHOT observations should more than triple the size of the sample
for which all of the important hot gas tracers are available, enabling us to
derive a truly global view of the hot ISM.
================================================================================
Proposal Category: SNAP
Scientific Category: ISM
ID: 8663
Title: Survey of SMC Planetary Nebulae: Nebular and Stellar
Evolution in a Low-Metallicity Environment
PI: Letizia Stanghellini
PI Institution: Space Telescope Science Institute

A survey of SMC planetary nebulae (PNe) is proposed to study the co-evolution
of the nebulae and their central stars, in an environment that is chemically
very metal poor. We will obtain STIS imaging and medium-resolution slitless
spectroscopy which will yield line fluxes and nebular morphologies in
important emission lines, plus magnitudes of the central stars. From these
data we will gather a harvest of information: the nebular size, morphology,
ionization structure, density, and mass; and the central star temperature,
luminosity, and mass. We will test the correlation found in the Galaxy of
nebular bipolarity with large progenitor star mass and with chemical
enrichment of the outer envelope during the prior AGB phase. These
relationships between PN and central star evolution will be pursued in the SMC
with a sample free of distance uncertainties and selection biases, and in a
metal-poor chemical environment that stands in sharp contrast to the Galaxy
and the LMC. The importance of this program is two-fold: We will determine the
late evolutionary paths of the most common stars in a galaxy that, in its
chemical content, mimics a young galaxy; and we will produce a sample of
extragalactic PN images and spectra that will far exceed in number the
galactic PNe already observed with HST, providing an homogeneous database for
testing the evolutionary implications of metallicity variations in stellar
evolution.
================================================================================
Proposal Category: SNAP
Scientific Category: SP
ID: 8664
Title: Structural Measurement of Globular Clusters in M31 and
NGC 5128: Stalking the Fundamental Plane
PI: William E. Harris
PI Institution: McMaster University

Globular clusters have amazingly simple structures that are well approximated
by isotropic, single-mass King (1966) models. All structural properties of a
King-model cluster follow from specifying its total luminosity L, central
concentration c, mass-to-light ratio M/L, and binding energy E_b. However, in
this four-dimensional space, real Galactic globulars inhabit only a remarkably
narrow region referred to as the fundamental plane (FP). Recently McLaughlin
(1999) has shown that clusters are confined to the FP through two extremely
well defined empirical relations, M/L=const and E_b~ L^2.1, leaving only the
two remaining parameters c and L to govern their scatter on the plane. These
results strongly constrain the cluster formation process; in particular, the
detailed nature of the E_b(L) correlation suggests that the star formation
efficiency in protoglobulars increased systematically with their mass. We
propose to use the STIS/CCD camera in SNAPSHOT mode to image a wide selection
of individual globular clusters in two other large galaxies (M31 and NGC 5128)
for measurement of their structural parameters (r_c, Mu_0, c). We will use
these to compute their binding energies and define the FP in these two
galaxies. Comparison with the Milky Way will then give us powerful new
information on just how ``universal'' the cluster formation process was in the
early protogalaxies.
================================================================================
Proposal Category: GO
Scientific Category: AGN
ID: 8665
Title: The Starburst - AGN Connection: The Nature of the UV-
bright Core in NGC 4303
PI: Luis Colina
PI Institution: Instituto de Fisica de Cantabria

NGC 4303 is to date the best example of the claimed starburst - AGN connection
in active galaxies. HST images of NGC 4303 have unveiled the existence of a
nuclear mini-bar (250 pc in size), centered on the unresolved (size <= 8 pc)
UV-bright core, itself connected with a star-forming mini-spiral (radius ~ 250
pc). The spiral consist of compact clusters (size <= 15 pc) of young stars (5-
25 Myrs). The UV-bright core is classified as a Seyfert 2 AGN but its UV
luminosity and optical properties are also compatible with the existence of a
young (~ 4 Myr) massive (~ 10^5 M_\odot) cluster of stars. We propose to
obtain STIS UV spectra of the unresolved core and the brightest knots in the
star-forming mini-spiral of NGC 4303. The spectra will be combined with
multifrequency data and evolutionary spectral synthesis models to: (1) pin
down the nature of the UV-bright core, i.e. AGN versus young massive stellar
cluster, (2) quantify the AGN and starburst energy contribution, (3) determine
the age and mass of the star-forming knots, and (4) establish an evolutionary
sequence of events within the bar - starburst - AGN scenario. The detection
of signatures of massive stars in the spectrum of the core of NGC 4303, would
demonstrate for the first time ever that a compact (<= 8 pc) massive stellar
cluster is located at the core of a Seyfert 2 galaxy and is, perhaps, its
dominant energy source.
================================================================================
Proposal Category: GO
Scientific Category: AGN
ID: 8666
Title: Outflows from the Disk Fueling the Massive Black Hole in
M87
PI: Holland Ford
PI Institution: Space Telescope Science Institute

The disk in M87 is a prototype for gas orbiting a massive central object.
Although the disk is rotating, its morphology and kinematics are far from
simple. A deep Halpha+N II HST image shows a trailing, three arm spiral
superposed on the underlying disk, and an extended system of filaments. The
NW filaments appear to connect directly to the disk. Ground-based and HST
observations suggest that some of the filaments originate in a bi-directional
wind emanating from the disk. Such a wind can carry away angular momentum,
enabling gas to flow through the resolved disk into the accretion disk around
the black hole. We propose high spatial resolution STIS spectroscopy aimed at
achieving the following scientific goals: 1) Determine if winds are carrying
angular momentum away from the disk, thereby enabling inflow and fueling of
the massive black hole, 2) Estimation of the rate of mass loss and angular
momentum loss from the disk, and 3) Use changes in the velocities and line
strengths at the positions of the spiral-like features in the disk to
determine if these are shocks where gas is flowing through a density wave.
Because small, 100-parsec scale gaseous disks like the one in M87 are common
in the centers of active galaxies, demonstration that a wind is removing
angular momentum from the M87 disk will have far reaching consequences.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8667
Title: Nuclear Stellar Disks in Early Galaxies: Black Hole
Masses and Disk/Bar/Bulge Evolution
PI: Walter Jaffe
PI Institution: Leiden Observatory

In an unbiased sample of nearby E/S0 galaxies we discovered 6 new stellar
nuclear disks, in addition to 3 discovered in earlier work. These disks are
ideal tools for measuring central black hole masses, and the one earlier case
studied spectroscopically, NGC 4342, showed an unusually high M_bh/M_bulge
ratio. Another, NGC 4570, shows a series of rings of anomalous color and
morphology which seem to be a fossils of an episode of mass accretion, bar
formation, dynamical resonances, and bar dissolution into a bulge. We propose
STIS spectroscopy and WFPC/2 imaging of an additional 4 of these galaxies to:
(1) test whether the unusual M_bh/M_bulge ratio is typical of these nuclear
disk galaxies and (2) search for additional ring/bar structures will help
determine the source of the accreted material and the time sequence of the
disk/bar/bulge/Black Hole fueling connection.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8668
Title: Spectroscopy of candidate, very massive, intermediate age
globular clusters in ESO 338-IG04
PI: Goeran Oestlin
PI Institution: Institut d'Astrophysique de Paris

The blue compact starbursting galaxy ESO 338-IG04 has been found to be very
rich in globular clusters (GCs) of varying age, from a few Myr to 10 Gyr.
Among low mass galaxies, it appears to be an extraordinary efficient GC
factory, and its GC richness is fully comparable to those of giant
ellipticals. An important GC formation event occured some 2.5 Gyrs ago. In
this age category we find cluster no. \#34, an unusually massive cluster with
\cal M > 10^7 \cal M_\odot. Here, we propose to observe this cluster, and two
other intermediate age massive GC candidates. The aim is to derive ages,
metallicities and internal extinction, in a self consistent way. This will
provide a test on the origin and chemical evolution of the host galaxy, and a
possibilty to assess the reliability of photometrically derived ages and
masses for young GC candidates in general. The latter point is important,
because GCs, beeing fossil starbursts, may be used to probe the starburst
history of galaxies in the universe. Also, beeing true single stellar
populations, massive (where number of stars are large and statisical
fluctuations small) GCs provide important tests for stellar evolution models.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8669
Title: Merger-driven evolution of galactic nuclei: observations
of the Toomre sequence
PI: Roeland P. van der Marel
PI Institution: Space Telescope Science Institute

Galaxy mergers are believed responsible for triggering starburst and AGN
activity in galaxies, and even perhaps transforming spiral galaxies into
ellipticals. Ground-based observations and numerical simulations have shed
light on these issues, but have not been able to adequately resolve the nuclei
of merging galaxies. However, it is these nuclei where most of the important
physical processes operate, and where a direct study of the stellar and
gaseous components yields crucial insight on any picture of merger-driven
galaxy evolution. We propose here to use HST to study the structural, star-
forming, and kinematic properties of the galactic nuclei in the `Toomre
Sequence' of merging galaxies, at unprecedented spatial resolution. Broad-band
WFPC2 images with F555W and F814W will be used in concert with narrow-band
HAlpha+NII images to study the connection between nuclear morphology and the
structure of the ionized gas. The two-dimensional velocity field of the
nuclear gas will be probed via medium resolution STIS G750M observations,
while lower resolution G430L spectroscopy will study the young and old stellar
populations in the merging nuclei. Our study will provide the first
comprehensive view of the physical conditions in strongly interacting and
merging galactic nuclei, and, in concert with our dynamical modeling, will
place strong constraints on theories of merger-driven activity and evolution
in galaxies.
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8670
Title: The Role of Polycyclic Aromatic Hydrocarbons in
Ultraviolet Extinction
PI: Geoffrey C. Clayton
PI Institution: Louisiana State University

We propose to use the STIS on HST to search for structure in the ultraviolet
interstellar extinction curve, with particular emphasis on a search for
absorption features produced by polycyclic aromatic hydrocarbons (PAHs). The
existence of these molecules in the interstellar medium has been postulated to
explain the infrared emission features seen in the 3-13 Mum spectra of
numerous sources. However, these features have stubbornly resisted
satisfactory identification. We propose to obtain high S/N UV spectra of
stars which are significantly more reddened than those observed in previous
studies. These data, which can now be obtained through the high sensitivity
of STIS and HST, will allow us to estimate the abundances of PAHs in the ISM,
to make identifications of individual PAH molecules and to put strong limits
on the role of PAHs in UV extinction. The observational program will be
guided by our ongoing laboratory studies of neutral and ionized PAHs at the
low temperatures characteristic of the interstellar environment. PAHs are of
importance because of their ubiquity and high abundance inferred from the
infrared data and also because they may link the molecular and dust phases of
the interstellar medium. A search for ultraviolet absorptions due to PAHs
could be a definitive test of this hypothesis and, if successful, can identify
the particular PAH species present; this is not possible from infrared data
alone.
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8671
Title: STIS Observations of a Magellanic Cloud Nova in Outburst
PI: S. N. Shore
PI Institution: Indiana University South Bend

We propose target-of-opportunity observations of a classical nova in the
Magellanic Clouds in the early stages of its outburst. Nova outbursts are
thermonuclear runaways triggered by accretion onto a white dwarf within a
close binary system. As such, nova systems are a possible evolutionary stage
on the way to a final accretion-induced collapse and a Type Ia supernova
explosion. The study of how the accreted mass is mixed, the nuclear
processing that occurs during the outburst, the energetics of the explosion,
and the determination of ejecta masses constrain models for SNe Ia
progenitors. The ultraviolet (UV) spectrum provides fundamental and unique
information on the expanding nova ejecta. We propose to obtain
spectrophotometric and line-profile information at sufficient resolution with
STIS to determine the abundances and mass of the ejecta as a function of
position in the nebula and, thereby, obtain a comprehensive picture of the
energetics of the outburst, which can be compared to multidimensional
hydrodynamic studies of nova explosions. Because novae are hot and have lines
from chemical elements that are only detectable in the UV, the STIS UV
capability is crucial for an analysis of nova ejecta. The nova will also
provide a background source for study of the Galactic and MC interstellar
media along the line of sight to the outburst.
================================================================================
Proposal Category: GO
Scientific Category: QAL
ID: 8672
Title: Establishing the Gaseous Phases of Galaxies Following the
Epoch of Star Formation
PI: Chris Churchill
PI Institution: The Pennsylvania State University

We propose an ambitious program designed to: (1) establish if high ionization,
metal--rich halos/coronae were in place as early as z~ 1, which would imply
that extended, early--epoch, galactic halos result from reprocessed galactic
gas and that the kinematics are mechanically driven; (2) obtain the first
comparison of the relative kinematics of low and high ionization species in z
~ 1 galaxies, covering a wide range of N(\HI) environments and Mg II
kinematic spreads up to ~ 400 kms; (3) discriminate between single--phase and
multi--phase ionization, and therefore spatial, absorbing structures (eg.\ Mg
II clouds embedded in diffuse high ionization halos); and (4) place
constraints on the gas--phase metallicites in early--epoch galaxies. We
propose to obtain STIS R=30,000 (Delta v = 10 kms) spectra of five bright
quasars, for which the FOS/ HST data are fully analyzed. Our observational
goal is to resolve the absorption profiles of several low, intermediate, and
high ionization species, including OVI,OI,NV,NIII,CIV,CIII,CII,[S II]V, [S
II]II, and [S II]I, in 18 Mg II absorption systems covering 0.5 <= z <= 1.3.
We incorporate our high signal--to--noise HIRES/Keck (Delta v=6.6 kms)
profiles of MgII,\MgI, and Fe II of the low ionization absorbing gas, and our
database of the absorbing galaxy luminosities, colors, and impact parameters.
================================================================================
Proposal Category: GO
Scientific Category: QAL
ID: 8673
Title: The Properties of Ly-Alpha Absorbers at Redshifts Between
0.9 PI: Buell Jannuzi
PI Institution: National Optical Astronomy Observatories

We propose to use STIS to obtain new Echelle resolution (10 km s^-1) spectra
of three bright quasars which, when combined with archived and scheduled
observations, will be used to characterize the properties of Ly-Alpha
absorbers in the redshift range 0.9 approximately 300 Ly-Alpha absorbers, comparable in size to some of the
samples being used successfully to characterize the properties of absorbers at
higher redshifts, is the immediate objective of this program. The physical
characteristics of the final sample will be compared to the expected
properties derived from analysis of the ever increasing number of simulations
of the IGM and Ly-Alpha absorbers at z~1 (e.g., Zhang et al. 1997; Dave et al.
1998; Riediger et al. 1998; and Theuns et al. 1998). While the simulations
have all managed to reproduce the general observed properties of z~3
absorbers, they make different predictions for these properties at z~1. These
differences arise because the expansion history of the universe and the rate
of structure formation depend on the values of Omega and Lambda, and both
affect the evolution of statistical properties of the absorbers. More
broadly, comparison between the properties at z~1 and those at higher
redshifts can test whether structure in the Ly-Alpha forest is evolving in the
manner predicted by gravitational instability theories.
================================================================================
Proposal Category: GO
Scientific Category: SF
ID: 8674
Title: STIS coronographic imaging of old PMS stars
PI: Anne-Marie Lagrange
PI Institution: Laboratoire d'Astrophysique de Grenoble

In the past decade, \cs (CS) disks of short lived dust and gas have been
evidenced around \ms (MS) stars (e.g. \bp). The dust and gas are probably due
to planetesimal collisions and/or comet evaporation. These so called ``second
generation disks'' are then believed to trace the history of planetary systems
formation, in a stage where planetesimals are numerous and planets may be
already formed, i.e. an evolved stage compared to the disks around young stars
such as Classical T Tauri stars, but yet prior to mostly dust free planetary
systems such as those revealed by radial velocity searches., We recently began
to investigate the missing link between MS and young stars CS environments by
searching for second generation disks of dust or gas around the few known old
+/-s stars and by modeling their CS environments. Our HST/NICMOS images
revealed a disk around HD141569 (10 Myrs), and possibly also (but still to be
confirmed) around HD100546 and HD135344. , We propose here to use the
unprecedent detection capabilities of STIS/CORON to get high signal-to-noise
(SN) images of HD141569 and HD135344. This will allow to study in much more
detail the HD141569 disk, to confirm or infirm the other disk, and to perform
fine modeling of the CS dust. This is a key step in the study of the complete
evolution of (proto)planetary systems, from the PMS to the MS stages.
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8675
Title: The Massive Star Content of NGC 6822
PI: Luciana Bianchi
PI Institution: The Johns Hopkins University

We propose to characterize the young, coeval stellar population discovered
with WFPC2 multiband imaging in a NGC6822 star forming region, with follow-up
spectroscopy of the massive star candidates. Photometry alone is not sensitive
to accurate measurements of temperature and extinction for stars hotter than
B2. Blue spectra will provide spectral type classification, and measurements
of the stellar temperature, which will allow us to construct meaningful H-R
diagrams. UV spectra will provide critical measurements of ionizing
luminosities, wind velocity and mass loss. STIS configurations allow a most
effective observing strategy: we will take UV spectra in slitless mode, and
the optical spectra with the STIS long slit in the G430L range, which will
also provide spatially resolved information on the surrounding parent nebula.
The UV plus optical spectra will yield a quantitative determination of all
stellar parameters, and of the extinction properties, in this extremely metal
-poor HII region. This study will provide a step forward in understanding how
massive star formation (initial mass function, radiative and dynamical
balance) and evolution depend on metallicity and other environmental factors.
Resolved studies of local starbursts provide a key to interpret active star-
forming distant galaxies. We also request WFPC2 parallel imaging to continue
our stellar population study.
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8676
Title: Halo Microlens Source Systems and their Backgrounds and
Reddening
PI: Kem Cook
PI Institution: Lawrence Livermore National Laboratory

The MACHO project is about to release 5.7 years of LMC data revealing ~ 20
candidate microlensing events, and suggesting the existence of dark objects in
the Galactic halo. We propose to obtain medium-deep broadband images of 8 of
the new candidate source stars. This will allow us to determine a) which star
was actually lensed, b) the amount of crowding in our ground-based frames, c)
if the stars are normal in the CMD, and d) if they lie preferentially at the
back of the LMC. This provides a clear test for microlensing by halo objects.
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8677
Title: Extragalactic Novae: the Maximum Magnitude - Rate of
Decline Relation in NGC 4472
PI: Laura Ferrarese
PI Institution: California Institute of Technology

The two goals of this proposal are: (1) to provide the first homogeneous
observational constraints on theoretical models for novae outbursts; and (2)
to assess the reliability of novae as standard candles. We propose to
accomplish these goals by using WFPC2 to collect well sampled light curves for
20-50 novae in the supergiant elliptical galaxy NGC 4472, the brightest galaxy
within 30 Mpc. Both the length of the observing window and the temporal
sampling of the observations are specifically designed to ensure that the
novae peak magnitudes and decline rates are measured accurately. These data
will be used to construct the first `Maximum Magnitude versus Rate of Decline'
(MMRD) relation for a galaxy beyond the Local Group. This relation is not
only a potentially powerful standard candle, but its shape and dispersion are
directly linked to physical parameters which govern the physics of novae
outbursts such as the white dwarf mass, temperature and mass accretion rate.
At present, it is impossible to investigate the universality of the MMRD
relation since there exist no more than 30 extra-galactic novae with well
sampled light curves (most in M31 and the LMC). Our short survey will
therefore double the sample of novae light curves accumulated during the past
century, and will provide the first strong observational constraints on
theoretical models of novae production and outburst.
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8678
Title: Galaxy Mass and the Fate of the ISM in Candidate Proto-
Spheroidals at z~0.2-0.4
PI: Rafael Guzman
PI Institution: Yale University

We propose to obtain STIS long-slit spectra for a sample of 5 faint blue
compact galaxies (BCGs) at z ~ 0.2 to 0.4. Despite being very luminous (M_B~-
20), BCGs have velocity widths Sigma <~ 60 kms, and half-light radii r_e <~
0.5'' (or R_e <~ 3Kpc). The small sizes and velocity widths suggest that BCGs
are low-mass stellar systems (Mla10^10M_\odot), while their very blue colors,
strong emission lines and low M/L-ratios indicate that they are undergoing a
major starburst. If the star-forming process halts after the current burst,
galaxy evolution models predict that BCGs will fade by ~3-4 magnitudes after a
few Gyrs to reach the low luminosities and surface brightnesses characteristic
of spheroidal galaxies. Thus we may be witnessing, in-situ, the last major
episode of star formation in today's dwarf, low surface brightness galaxies
such as NGC 205. Spatially-resolved spectroscopy will allow us to perform
unique tests of this evolutionary scenario by providing: i) measurements of
rotational velocities --rather than Sigma-- to determine whether BCGs are
indeed low-mass stellar systems; and ii) evidence for any substructure in the
line emitting region associated to SN-driven galactic winds. This information
will shed light on the ultimate fate of the ISM in BCGs, and thus on whether
it is reasonable to expect that no further star formation episodes will occur
after the current burst.
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8679
Title: Constraining the Age of the Oldest Stars from the White
Dwarf Cooling Sequence in M4
PI: Harvey Richer
PI Institution: University of British Columbia

We propose to search for the oldest and hence coolest white dwarfs (WDs) in
M4, the nearest Galactic globular cluster to the Sun. New models for cooling
hydrogen white dwarfs predict that their colors should become bluer, rather
than redder, with increasing age. Our goal is to test these models and at the
same time constrain the age of M4. This would be the first test of globular
cluster ages ever done that would not depend on the timescale to exhaust the
hydrogen core of a main sequence star. New revised distance moduli and stellar
evolution models now support an age of 11.5+/- 1.5 Gyr for the globular
clusters. If we can reach V=30, we can solidly measure the turnover in the M4
WD luminosity function for an age of 12 Gyr, and we will get meaningful
constraints on larger ages. The images will be taken in a single field of the
cluster using the WFPC2 and the F606W and F814W filters. If we are successful
in reaching the termination point of the WD cooling sequence in this cluster
we will be able to derive an accurate estimate for the age of the cluster and,
with only a mild extrapolation, for the Universe itself. Further, if it is
indeed correct that the lensing objects in the various microlensing
experiments in the direction of the Magellanic Clouds are old WDs, then these
data will also prove to be critical in guiding the extensive searches that are
now being carried out to find local examples of these MACHOs.
================================================================================
Proposal Category: GO
Scientific Category: SS
ID: 8680
Title: The Asymmetric Atmosphere of Uranus
PI: Heidi Hammel
PI Institution: Space Science Institute

We propose to image Uranus as the planet plunges toward equinox in 2007.
Recent HST images during this unique epoch (6818: Hammel, Lockwood, and Rages;
7429: Tomasko and Karkoschka; 7885: Hammel, Karkoschka, and Marley) have
revealed: (i) strongly wavelength-dependent latitudinal structure, (ii) the
presence of numerous visible-wavelength cloud features in the northern
hemisphere, (iii) zonal winds which may deviate from the smooth profile
implied by the Voyager observations in 1986, and, (iv) in the near-IR,
discrete features northward of +25degrees\ that have the highest contrast ever
seen for a Uranian cloud (Karkoschka 1998, Science 393, 765-767; Hammel Etal
1999, submitted to Icarus). Specific scientific issues we will address with
new observations are: whether the northern features are indicative of
intrinsic change or result simply from a change of viewing angle; the shape
and stability of the zonal wind profile; and the source of the as-yet
unexplained variations of the atmospheric reflectivity. When possible,
observations will be coordinated with ground-based imaging, spectroscopy, and
photometry. This period approaching equinox is the first opportunity (in the
era of modern instrumentation) to examine the far regions of the northern
hemisphere on Uranus.
================================================================================
Proposal Category: SNAP
Scientific Category: AGN
ID: 8681
Title: A Snapshot Survey of Variability of Narrow and Broad
Associated Absorption Lines in Quasars
PI: Jane Charlton
PI Institution: The Pennsylvania State University

Variability in the strength of absorption lines in quasar spectra is
definitive proof that we are observing material that is physically associated
with the quasars. We propose to conduct a STIS snapshot survey to provide
second epoch observations of 37 quasars with narrow associated (Delta v<5000
kms) or broad absorption lines (NALs and BALs), previously observed with the
FOS. At high redshift several intrinsic NALs and about two thirds of BALs are
known to vary, often in accord with continuum variability. The timescales
decrease with increasing quasar luminosity. The low-redshift sample of
quasars in the FOS archive includes a larger fraction of nearby low-luminosity
quasars. Thus it may show more extreme variability in intrinsic absorption
lines than the high redshift sample. The present study will provide: (1) an
estimate of the fraction of quasars that have intrinsic NALs, (2) a lower
limit on the fraction of intrinsic NALs and of BALs that are variable and (3)
an indication of the relationships between continuum, emission line, and
absorption line variability in various chemical species. More importantly,
this snapshot survey will produce a database of variable low-z NALs and BALs
for studies at higher temporal and spectral resolution. Well resolved time
variability and partial coverage analysis of multiple chemical transitions
in these quasars may well provide the most detailed views yet of outflows
from the central engines.
================================================================================
Proposal Category: SNAP
Scientific Category: COS
ID: 8682
Title: A snapshot study of 0 PI: Stephen Serjeant
PI Institution: Astrophysics Group, Imperial College

The observational constraints on the cosmic star formation history is
currently among the most active fields in observational cosmology. The most
widely used tracer of the comoving volume-averaged star formation rate (SFR)
is the UV luminosity density, which early results found to peak at z~1-2. The
apparent identification of the primary epoch of metal production and star
formation in the Universe led to intense theoretical and observational
interest. Nevertheless, and remarkably for such a fundamental observation,
little is known about the history of star formation in the Universe beyond its
global average. Also, obscuration corrections are critical, and the UV
luminosity is highly sensitive to these dust corrections. The most ideal
obscuration-independent starburst selection is the decimetric radio flux,
which measures both obscured and unobscured star formation. Here we propose to
extend our cycle 8 program of WFPC2 F814W snapshots of sub-mJy starbursts,
selected at low radio frequency to avoid AGN and provide a robust SFR
conversion. We will greatly extend our luminosity and redshift range, to
determine the evolving morphologies and effects of obscuration in the galaxies
which dominate the cosmic SFR at 0 likely high-z counterparts of local IR-luminous / ultraluminous galaxies.
================================================================================
Proposal Category: SNAP
Scientific Category: GAL
ID: 8683
Title: Imaging of brightest cluster galaxies: the high end of
the black hole mass distribution
PI: Roeland van der Marel
PI Institution: Space Telescope Science Institute

Kinematic black hole (BH) detections in galaxies indicate that the mass \Mbh
correlates with both optical luminosity L and radio power P. However, these
quantities are themselves not tightly correlated, suggesting the existence of
a multi-variate relation between \Mbh, L and P. To study this relation we
propose a WFPC2 I-band snapshot survey of brightest cluster galaxies (BCGs).
BCGs have a nearly universal optical luminosity, but their radio power varies
by >10^4. We will infer the nuclear surface brightness profiles and central
cusp slopes, which yield photometric BH mass determinations using Young's
adiabatic BH growth models. Such determinations agree well with kinematical
measurements (van der Marel 1999), so this provides an efficient method to
study a large sample without time-consuming spectroscopy. We focus on the
galaxies in the volume limited sample (z <= 0.05) that we have studied from
the ground at optical (Lauer & Postman) and radio (Owen, O'Dea) wavelengths.
We will use the HST data to estimate the scatter in cusp slope and \Mbh at
fixed optical luminosity, and its correlation with radio power. The images
will also provide an important database for studying the relation between
satellite accretion, multiple nuclei and the brightness profiles of BCGs. The
dataset will be generally useful for studies of many kinds, and for maximum
benefit to the community we give up all proprietary rights.
================================================================================
Proposal Category: GO
Scientific Category: AGN
ID: 8684
Title: Emission Lines from Photoionized Accretion Disks and
Winds in AGNs
PI: Michael Eracleous
PI Institution: The Pennsylvania State University

A fundamental gap that remains in our knowledge of AGNs is the origin and
dynamics of the gas that produces their broad optical and ultraviolet emission
lines. In most other accreting systems, emission lines are demonstrably
linked either to the accretion disk or to an accretion-disk wind; these are
both leading hypotheses for the origin of emission lines in AGNs as well. We
can test both of these models by exploiting the extreme properties of the so-
called ``double-peaked emitters.'' These very broad double-peaked emission
lines have proven to be uniquely capable of testing dynamical models, and as a
result several theories are no longer considered likely. The two major
theories that are the subject of this proposal require HST for their
evaluation because they make contrasting predictions about the differences
between the Balmer-line and UV resonance-line profiles. In fact, there is good
evidence that both photoionized disk atmospheres and radiatively driven winds
contribute to observed emission lines in varying degrees. We have preliminary
evidence that points toward luminosity as the primary factor which controls
the relative importance of disk and wind. By observing a set of four more
double-peaked emitters covering a wide range of luminosity, we will test the
hypothesis that photoionized disk atmospheres dominate line production at low
luminosity and winds dominate at high luminosity.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8685
Title: Isolated compact stellar systems in the Fornax Cluster
PI: Michael Drinkwater
PI Institution: University of Melbourne

We have discovered a new population of compact objects in the centre of the
Fornax Cluster. These objects have spectra typical of old stellar systems, but
are unresolved in ground-based imaging. They are all at least 10 times more
luminous than any Galactic globular clusters, but fainter than any known
compact dwarf galaxies. They may be a new class of intermediate object,
neither globular clusters nor dwarf galaxies but something in between. We
request HST imaging of a sample of these objects to measure their light
profiles and determine their structure. We need the high resolution imaging of
HST to measure the radii of these objects which we will combine with ground-
based spectroscopy to determine their mass-to-light ratios. This will allow us
to compare them to known compact objects such as globular clusters and the
nuclei of dE galaxies to establish if they do indeed represent a new class of
hitherto unknown stellar system.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8686
Title: LINERs in Early-type Galaxies: Ionized by the UV-upturn
Population ?
PI: Paul Goudfrooij
PI Institution: Space Telescope Science Institute

Our recent ground-based imaging and spectroscopic surveys have revealed the
presence of extended ionized gas with LINER spectra in a large fraction (60--
70\ galaxies. In order to provide clues to the nature of this gas, we propose
to obtain deep STIS far-UV images of a suitable sample of 8 nearby
ellipticals and E/S0s to test in detail whether the ``UV upturn'' population
in early-type galaxies (AGB-manque stars and post-AGB stars) is a viable
source of ionization for the observed ionized gas in ``normal'', radio-quiet E
and E/S0 galaxies. STIS is the first and only instrument able to provide data
to study the radial distribution of the UV-bright population, as its influence
is expected to show up only in the central few hundred parsec. The observed
radial (far-UV - optical) color gradients will be compared to detailed
spectrophotometric synthesis models to deduce the number of ionizing photons
and their spectral energy distribution, from which we will deduce the expected
emission-line spectra and H-alpha\ luminosities as a function of radius. We
also request narrow-band WFPC2 images for 5 galaxies in our sample to derive
the central radial surface brightness profile of the H-alpha+N II\ emission
which can be directly compared to the model prediction. The other 3 galaxies
have such WFPC2 data already available in the archive.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8687
Title: Elliptical Galaxies With Nuclear Disks of Stars: Black
Hole Search and Stellar Populations
PI: John Kormendy
PI Institution: University of Hawaii

def\ts def\mbhM_o We propose STIS spectroscopy of the galaxies NGC 3706 (E3)
and NGC 4486A (E2) to search for supermassive black holes (BHs). NGC 3706
contains a bright, edge-on nuclear disk of stars. Therefore we can measure
the BH mass \mbh\ as easily as in a galaxy with a gas disk but without
uncertainty about whether the motions are affected by non-gravitational
forces. NGC 4486A, like NGC 4486B, is a dwarf elliptical companion of NGC
4486 (M\ts87) with signs of an unusually massive BH. Keck spectroscopy shows
that its velocity dispersion Sigma ~eq 160 km s^-1 is abnormally high for a
dwarf galaxy of absolute magnitude M_B ~eq -17.5. We want to know whether it
is an exception to the correlation of \mbh\ with bulge luminosity. We propose
low-resolution Mg I b spectroscopy of the above galaxies and NGC 5845 to
compare the stellar populations in their nuclear disks with those of their
bulge components. Many ellipticals contain dust disks or stellar disks. NGC
4486A and NGC 5845 are ``Rosetta stone'' objects that contain both. They can
provide direct evidence that gas disks grow stellar disks near the centers of
early-type galaxies and thereby secularly increase the cuspiness of the mass
distribution. The timescale of this process is unknown. Our spectra would
tell us the relative ages of the stellar disks and bulges in two ellipticals
that are caught in the act and in one with a remarkably prominent and fully
formed stellar disk.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8688
Title: Gamma-ray bursts: discovering the progenitors and
understanding the explosion
PI: S. R. Kulkarni
PI Institution: California Institute of Technology

Gamma-ray burst astronomy, one of the most active and exciting frontiers in
astrophysics, is now entering a critical stage -- with dramatic leaps in our
understanding of these events, as well as new discoveries imminent. In the
upcoming year, improvements in triggering and positioning accuracy provided by
the SAX and HETE-2 gamma-ray satellites will allow entirely new classes of
events to be studied. Given the recent progress in this field, we are now in
a position to design precision, broadband measurements that can provide
quantitative information on the as-yet unknown energy sources, the explosion
geometry, and the surrounding medium. In particular, the growing evidence of
an intimate connection between SNe and GRBs can be definitively tested. We
propose a set of HST TOO and standard observations, synergistic with ground-
based radio, IR and optical observations, as well as CXO measurements,
designed to answer the outstanding and fundamental questions in GRB astronomy.
We believe this program will dramatically alter our understanding of these
events, and will become a significant part of the scientific legacy of
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8689
Title: UV extinction in Dusty Ellipticals
PI: James Rhoads
PI Institution: Kitt Peak National Observatory

We propose UV spectroscopy of bright inner parts of two dusty elliptical
galaxies to study their ultraviolet extinction, in particular the 2175
Angstrom bump. These galaxies are selected from a sample of dusty ellipticals
having very different, and in some cases highly chromatic extinction law in
the visible (Goudfrooij et al. 1994). A chromatic extinction law requires
either a deficiency of carbonaceous grains or a smaller typical grain size
relative to Milky Way dust. The strength of the 2175 Angstrom\ feature, which
is due to carbon grains, is the best way to distinguish between these two
possibilities. A smaller typical grain size can come about due to grain
erosion by x-ray gas, or due to lack of grain growth in dense molecular
clouds. A deficiency of carbonaceous grains could come about due to chemical
sputtering by hydrogen or due to reduced production of carbonaceous grains by
aging stellar populations. These observations will distinguish between
different physical explanations for anomalous optical extinction properties,
and will thereby constrain the evolutionary history and physical conditions in
the interstellar media of elliptical galaxies.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8690
Title: The Central Region of NGC4696: Manifestation of the
Physics of Mergers?
PI: William Sparks
PI Institution: Space Telescope Science Institute

Massive, dominant ellipticals with attendant emission-line gas, dust and hot,
heavy X--ray emitting coronae lie at the very centers of galaxy clusters. The
physics of these complex, high pressure regions remains controversial: Are
cooling flows responsible? Do mergers dominate, with massive accretion events
triggering an array of phenomena? Is the AGN crucial? A major impetus to
understanding the physics of these regions will come with Chandra. NGC4696 in
the Centaurus galaxy cluster is archetypal. WFPC2 images have shown a dramatic
bifurcation between gas and dust. The nucleus itself is seen to be a compact
triple, with two blue components straddling a third red one. We propose to
obtain STIS long-slit spectra (\romannumeral1) along a line-emission filament
and (\romannumeral2) along a dust filament: are we witnessing physical
separation of gas and dust, as in comet ion/dust tails, due to late stage
merger physics; or are very high velocities, due to powerful AGN influences,
shifting emission lines out of filters? Is the HAlpha+NII filament a shock,
responsible for the known off-center X--ray peak? (\romannumeral3) A third
spectrum will be across the compact 0.26'' triple nucleus: is it a multiple
nucleus confirming the merger scenario; or a disk around a black-hole,
allowing mass determination; or the first double optical synchrotron jet; or a
gravitational lens? A wealth of vital physical and kinematical data will
result from these carefully selected spectra.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8691
Title: Calibrating the Cosmic Meter Stick: The Distance to the
LMC Using Eclipsing Binaries
PI: Edward Guinan
PI Institution: Villanova University

The LMC distance is crucial for the calibration of the Cosmic Distance Scale.
However, there is considerable disagreement about this fundamental
measurement, with discrepancies among different methods of ~ 10\ immune from
zero-point uncertainties plaguing less direct methods, we recently determined
an accurate distance (m-M = 18.30 +/- 0.07 mag.) to the LMC eclipsing binary
(EB) HV2274. This distance was derived from ground-based light curves, HST/FOS
spectrophotometry, and GHRS radial velocity data. We propose HST/STIS
observations of three additional LMC EBs, carefully chosen from the large
MACHO and EROS surveys, to determine more accurately the LMC distance. These
detached, uncomplicated EBs, in the Bar or 30 Dor region, minimize corrections
to the LMC centroid. HST/STIS low-dispersion spectrophometry (115 - 580 nm)
will be used to determine T_eff and E(B-V). STIS/G140M observations yield
accurate radial velocities of these double-line systems which, when combined
with the light curves and temperatures, yield the stellar radii and
luminosities, and distances. These data form the core of this program to
determine the LMC distance, thereby firmly establishing the length of the
Cosmic Meter Stick to better than 2\
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8692
Title: Search for an Optical Counterpart to the Central X-ray
Point Source in Cas A
PI: Robert Fesen
PI Institution: Dartmouth College

First-light Chandra X-ray Observatory images have uncovered a central point-
like source in Cas A, the Galaxy's youngest known supernova remnant (SN 1680).
The object lies within 5'' of the remnant's estimated expansion center and is
presumably either the remnant's neutron star or black hole. Preliminary
analysis of the source's ACIS spectrum indicates Si (and possibly S) emission,
not unlike that seen in the remnant's ejecta, suggesting possibly an accretion
disk of fall-back SN debris. If this spectral analysis holds up, there is then
a good chance of detecting an optical emission line counterpart. We propose
to obtain deep `white light' STIS images of the Cas A center during five LOW
background orbits to search for an optical candidate down to ~ 29.5 mag.
Complementary WFPC2 images of Cas A which are sensitive to ejecta line
emission and already scheduled as part of a Cycle 8 program will be combined
to yield spectral information on all but the faintest sources. These data will
constrain the point source's nature through limits on its X-ray/optical flux
ratio, color properties, and the presence of any extended emission structure.
If a sufficiently bright optical source is found coincident with the X-ray
position, five additional orbits (TOO) are requested for low-dispersion STIS
spectra to search for optical line emission.
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8693
Title: Interstellar Boron & Oxygen Abundances in the Cep OB2
Association: Probing Neutrino Nucleosynthesis
PI: Verne V. Smith
PI Institution: University of Texas El Paso

A specific nuclear process associated with core-collapse supernovae involves
the inelastic scattering of neutrinos (produced as a result of the core
collapse) off of abundant nuclei in the outer layers of the dying star. Two
relatively low-abundance elements, boron and fluorine, have been suggested to
owe some uncertain fraction of their cosmic abundances to this process. In
the case of boron, the dominant isotope is ^11B, and neutrinos interacting
with ^12C can lead to its synthesis. Fluorine-19 is the only stable F isotope
and it can be produced by neutrino scattering removing a proton from ^20Ne.
Competing processes can also synthesyze these elements: cosmic-ray spallation
reactions for B and shell He-burning in AGB stars for F. In order to gauge
the importance of neutrino nucleosynthesis in the chemical evolution of the
Galaxy, we will use HST with STIS to determine interstellar B and O abundances
in the gas associated with the Cep OB2 association (using the B II
1362Angstrom\ and O I 1356Angstrom\ lines). These results will be combined
with observations of interstellar F I along the same lines-of-sight obtained
with FUSE (fluorine can only be compared directly to boron using interstellar
lines and interstellar F is only observable with FUSE). The derived F/O and
F/B ratios in Cep OB2 will allow us to determine the relative importance of
neutrino nucleosynthesis to the origins of B and F.
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8694
Title: Probing the Galactic Halo and Beyond with Young
Supernovae
PI: George Sonneborn
PI Institution: NASA's Goddard Space Flight Center

We propose a Target of Opportunity program to obtain STIS echelle spectra of a
bright new supernova (V<= 14) to characterize the ionization state, gas-phase
abundances, depletion on dust grains, metallicity, and gas kinematics in the
Galactic halo, the ISM and halo of the SN's host galaxy, and, if the
properties of the sightline are favorable, in the intervening intergalactic
medium. The principal spectral region for this study is the far ultraviolet
(\wl <1700Angstrom), which provides a comprehensive set of lines to study the
hot, warm, and cool phases of the ISM. New core-collapse supernovae, with
their strong, nearly featureless UV continua, provide outstanding
opportunities to obtain high-quality absorption line spectra of the gas on the
line of sight to the SN, but only if the observations are executed within ~1
week of outburst. Our team has the experience and extensive ground-based
support to promptly assess the suitability of each newly-discovered supernova
for this program and to quickly provide all the necessary data to rapidly
execute the observations. This proposal is a continuation of our Cycle 8 TOO
program, for which we await a suitable target.
================================================================================
Proposal Category: GO
Scientific Category: QAL
ID: 8695
Title: The Nature and Distribution of O VI Absorbers in the
Vicinity of Galaxies
PI: Todd Tripp
PI Institution: Princeton University Observatory

Hydrodynamic cosmological simulations predict that at z ~ 0, up to 50\ of the
baryons are in a shock-heated gaseous phase at 10^5 -- 10^7 \ ^degreesK. Such
gas may be easiest to detect via O VI absorption lines in the spectrum of a
background QSO. We have recently discovered several low redshift O VI
absorption line systems in the vicinity of groups of galaxies. In some cases
these absorbers are highly ionized, and the O VI lines can be quite weak. In
one case, low and intermediate ionization stages are detected, as well as O
VI, with complex velocity structure. Here we propose to study PG1259+593 (z_
Q = 0.472) with the STIS E140M echelle mode to substantially improve the
statistical base of observed O VI absorbers (including weak lines) for
comparison with the cosmological models and to constrain the physical
conditions and abundances in these systems and their relationships with
galaxies. We will also obtain follow-up observations of PG0953+415. With
these observations we will (1) measure the number of O VI absorbers per unit
redshift (dN/dz) with a limiting equivalent width of W_Lambda ~25 mAngstrom ,
(2) examine whether the O VI absorption arises in photoionized, collisionally
ionized, or multiphase gas, (3) estimate the absorber metallicities, and (4)
study the dependence of the absorber properties on the proximity of luminous
galaxies. These observations will be useful for testing predictions from the
cosmological models.
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8696
Title: Disentangling the Bulge and NGC 6528 - a proper motion
study
PI: Sofia Feltzing
PI Institution: Lund Observatory

We propose to obtain second epoch WFPC2 observations of the Galactic globular
cluster NGC 6528. These will be used to obtain proper motions of the cluster
relative to the background bulge field and thus provide, for the first time, a
colour-magnitude diagram of NGC 6528 free from background stars. NGC 6528 is
perhaps the most metal-rich globular cluster known and as such serves as an
invaluable template for calibrating and understanding metal-rich stellar
populations in extra-galactic bulges and disks, as well as serving as a
template in studies of our own Galactic Bulge. Observations of this cluster
are, however, severely hampered by it being superimposed on and physically
close to the Galactic Bulge itself, resulting in a colour-magnitude diagram
made up of Bulge and cluster stars. Thus the images currently available in the
HST-archive are of limited, if any, use as a template for metal-rich stellar
populations. Proper-motion studies of globular clusters, eg. NGC 6379, have
proved extremely efficient in cleaning the CMD from field stars.
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8697
Title: Stellar Populations in the Disk-Halo Interface of NGC 55
PI: Annette Ferguson
PI Institution: Institute of Astronomy

The disk-halo interface is where the global effects of stellar feedback on the
ISM are expected to be most pronounced. Our deep ground-based emission--line
images of the nearby, edge--on SBm galaxy NGC 55 provide a particularly
spectacular example of this phenomenon. In addition to numerous supergiant
ionized filaments and shells, our images also reveal the surprising discovery
of several candidate HII regions located at significant heights (1--2 kpc)
above the disk plane. We have obtained high-resolution ground-based broad-
band images for the brightest of these candidate HII regions, revealing
several underlying blue continuum sources, supporting the idea that such
regions might be the site of in situ star formation in the disk--halo
interface. If recent star formation has occurred in these clumps, it would
have extremely important implications for understanding the disk--halo
connection in galaxies. Further, if this is not an isolated event, there
should be a faint background thick disk/halo. We propose to obtain WFPC2 UVI
images of these candidate HII regions to resolve the embedded stars that
appear to be present, together with parallel STIS observations to
investigate a possible background thick-disk/halo stellar population, about
which there is little information in very late-type disk systems, and which
will place our targetted WFPC2 HII region
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8698
Title: Identification of the Galaxy's Missing Mass
PI: Jeremy Mould
PI Institution: Australian National University

The nature of dark matter is one of the key astrophysical questions of the
day. The existence of dark matter and its dynamical dominance in the outer
parts of our Galaxy and spiral galaxies with flat rotation curves is well
established. The MACHO project has identified ~half of the Milky Way's dark
matter with stellar objects of ~0.5 M_\odot, probably white dwarfs. But the
location of the microlensing in the halo is disputed. Ibata et al (astroph-
9908270) have detected two candidate halo white dwarfs of L/L_\odot ~ 10^-5 in
the Hubble Deep Field with 25 +/- 5 mas/year proper motions. They argue that
this could be the missing mass. We propose to make second epoch observations
of 20 WFPC2 fields in the Groth parallel program. If Ibata et al are correct,
we expect to see five times the number of white dwarfs, at half the distance,
with twice the proper motions, and ~three times the time baseline. The angular
shift of these objects will be ~300 mas, readily detected with WFPC2. In
addition, the detected objects will be bright enough for low dispersion
spectroscopy with large telescopes. If we confirm the Ibata et al result,
quantitative constraints will be put on the fraction of the Galaxy's missing
mass in this new stellar population.
================================================================================
Proposal Category: GO
Scientific Category: SS
ID: 8699
Title: The Origin of Short-Period Comets
PI: Philippe LAMY
PI Institution: Laboratoire d'Astronomie Spatiale

Following our recent success in detecting and characterizing eight cometary
nuclei with the HST and our approved program to detect 14 nuclei currently
underway in cycle 8, we propose a major program to determine the basic
physical properties of a large fraction of the population of short-period
comets. By acquiring statistically significant data, we can study the origin
of this family of comets and test the hypothesis that they are collisional
fragments from the Kuiper Belt Objects. Our technique takes advantage of the
high resolution of the PC2 to clearly distinguish the nuclei from the
surrounding comae provided they come within ~2.75 AU from Earth. Cycle 9 is
exceptionally favorable as 14 short-period comets meet this criterion. By
observing each nucleus eight different times, we will construct a light curve
from which we can derive the shape and rotation period. Observations will be
made through several filters (some combination of U,B,V,R,I depending on the
brightness) to obtain unique color information. If appropriate, corrections
will be applied to the measured sizes to remove the effect of erosion and
retrieve the ``original'' size distribution function. The results on the
size, shape, rotation period, and color to be obtained during this survey will
significantly contribute to the database of the physical properties of
cometary nuclei, nearly doubling the amount of reliable information currently
available.
================================================================================
Proposal Category: SNAP
Scientific Category: AGN
ID: 8700
Title: A STIS Spectroscopic Snapshot Survey of 3CR Radio
Galaxies : The Nature of the Unresolved Nuclei
PI: Andr'e R. Martel
PI Institution: The Johns Hopkins University

The 3CR Snapshot Survey, conducted with HST in Cycles 4-8 in broad-, LRF, and
UV/MAMA filters, has revealed the existence of unresolved nuclei or spikes in
36 ellipticals ellipticals with z<0.25. These are found in both FR I and FR II
radio types, over a wide range of radio luminosities and emission-line
properties. In this project, we propose to perform STIS snapshot long-slit
spectroscopy of these nuclei over 2900-10300 AA\ to classify them (QSO, NLRG,
BLRG, BL Lac, \ldots) and establish their AGN characteristics down to the
lowest nuclear luminosities, while still within powerful 3C radio galaxies.
Our primary goals are : (1) to test unification schemes by identifying
previously undetected signatures of low-level AGN/QSO activity in their
spectra in the form of weak, broad emission lines, featureless continua, and
UV excess, (2) to constrain the FR I/BL Lac connection by measuring the
relative contribution of thermal (starburst), non-thermal (optical
synchrotron), and line emission, and (3) to perform line and continuum
diagnostics to determine the dominant ionization mechanisms in the
circumnuclear regions (tenths of arcseconds) and the role of dust extinction
in the NLRGs and BLRGs in the form of geometrically thick or thin tori and
foreground dust.
================================================================================
Proposal Category: SNAP
Scientific Category: CS
ID: 8701
Title: Multiplicity among Very-Low Mass Stars and Brown Dwarfs
in Alpha Persei and the Pleiades
PI: Eduardo Martin
PI Institution: Caltech

Open clusters provide excellent hunting grounds for brown dwarf (BD) searches.
The AlphaPer and Pleiades clusters are young (80--120 Myr), nearby (120--175
pc), and have low extinction. They are cosidered to be the best-suited places
to study the Substellar Mass Function (SMF). A dozen of cool faint AlphaPer
and Pleiades members have been confirmed as ``bona-fide'' BDs with the
lithium test. By comparison with those, about 60 very good cluster BD
candiates are currently known. The Pleiades SMF obtained using the most recent
deep large CCD surveys indicates that BDs are quite numerous but do not make a
significant contribution to the total cluster mass. One of the main
uncertainties of the SMF is the effect of binary corrections. We propose a
WFPC2 search for faint companions to very low-mass cluster stars and BDs. We
will use any identified companions to provide empirical constraints on BD
evolutionary models, to test our ideas about fragmentation in molecular
clouds, and to correct the SMF. The sensitivity of WFPC2 shows that we can
readily detect secondaries with masses of about 25 Jupiters orbiting at about
40 AU from our targets. Companions with masses of about 15 Jupiters can be
detected at separations of 80 AU.
================================================================================
Proposal Category: SNAP
Scientific Category: ISM
ID: 8702
Title: The Most Elusive Nuclei of LMC Planetary Nebulae
PI: Richard Shaw
PI Institution: Space Telescope Science Institute

We propose to carry out a SNAPSHOT survey of the faintest nuclei of planetary
nebulae (PNe) in the LMC. This program will be a crucial follow-on to a Cycle
8 SNAPSHOT of LMC PNe; here we plan to observe the faintest or most obscured
nuclei to determine their evolutionary state to an accuracy not possible in
the Galaxy. These faintest central stars are predicted to be among the most
massive nuclei, and owing to the typically advanced age of the surrounding
nebulae, are the most sensitive discriminants for validating the post-AGB
evolution timescales predicted by theory. The key to calibrating the
evolutionary timescales is to relate them to the nebular dynamical (expansion)
timescale. By studying the parallel evolution of nebula and star it will be
possible to gain a firm understanding of the complex interplay between the
progenitor mass, and the post-AGB evolution of the nebula and the central
star.
================================================================================
Proposal Category: GO
Scientific Category: AGN
ID: 8703
Title: A Spectacular Post-Starburst Quasar and the AGN--
Starburst Connection
PI: Michael Brotherton
PI Institution: Lawrence Livermore National Laboratory

We propose broad-band imaging of the spectacular post-starburst quasar UN
J1025-0040 (V=19, z=0.634). The optical spectrum is a chimera, dominated in
the blue by light from a quasar, and dominated in the red by light from a 400-
Myr-old starburst with a mass possibly as much as 10^11 M_SUN. The total
energy budget of both sources appears similar, 10^11.6 L_SUN. The extended
fuzz of the host galaxy is asymmetric toward a nearby companion (dominated by
an 800-Myr-old starburst), signifiying some kind of interaction. The
relationship between the starburst and the quasar is unclear. The resolution
of the Hubble Space Telescope is required to determine if the starburst is
located in a second nucleus of a merging system, a circumnuclear ring, or some
more complex geometry. The extreme nature of this post-starburst quasar
provides a unique test case to investigate the connection between galaxy
interactions, starbursts, and AGN activity.
================================================================================
Proposal Category: GO
Scientific Category: COS
ID: 8704
Title: The Distance to the Type Ia SN 1999by in NGC 2841
PI: Peter Garnavich
PI Institution: University of Notre Dame

HST is unique in its powerful ability to directly calibrate type Ia supernova
luminosities by observing Cepheid variables in their host galaxies. Still,
only five SNIa with light curves obtained photoelectrically have had their
hosts distances measured and most of these are slow-declining, over-luminous
events. We propose to estimate the distance to SN 1999by, a sub-luminous type
Ia, by obtaining light curves of Cepheid variables we discover in NGC 2841.
The Cepheid distance to SN 1999by combined with the previously measured SNIa
will be used to calibrate all ~40 well-observed SN Ia events in the Hubble
flow to estimate an unbiased Hubble constant. Because intrinsically faint SNIa
are most often found in E/S0 galaxies, SN 1999by provides the only case where
Cepheid calibration of a sub-luminous SNIa is possible.
================================================================================
Proposal Category: GO
Scientific Category: COS
ID: 8705
Title: External Shear in the Time-Delay Lens RX J0911+05
PI: Jens Hjorth
PI Institution: University of Copenhagen

We propose to map the mass distribution in the vicinity of the multiple QSO
system RX J0911+05 using weak gravitational lensing. This object has emerged
as one of the most promising candidates for a cosmological determination of
the Hubble constant using time delay measurements. There is evidence that a
high-redshift group or cluster of galaxies (z=0.6--0.8) acts as the source of
a very large external shear (Gamma > 0.15), affecting the lens potential. Deep
WFPC2 images will allow us to directly measure this shear from the distortions
of faint background galaxies. Such data are essential for producing a reliable
mass model of the system which, in combination with the newly measured time
delay, will provide the best constrained mass model for a multiple QSO, hence
leading to an accurate cosmological estimate of the Hubble constant.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8706
Title: Phoenix: ``halo/disk'' structures in dwarf galaxies
PI: Antonio Aparicio
PI Institution: Instituto de Astrofi sica de Canarias

Hierarchical clustering scenarios for galaxy formation predict that dwarf
galaxies are the first to be formed and that they are building blocks of
larger galaxies. We propose here to measure the spatial structure and the
stellar age and metallicity distribution of the Phoenix dwarf galaxy to give
support or reject such scenarios. The kind of detailed study we propose can
only be carried on in nearby dwarfs and using the HST. We intend to obtain
very deep V and I color-magnitude diagrams reaching the oldest MS turn-offs of
a central and an outer field of Phoenix. Applying our techniques based on
synthetic color-magnitude diagrams, we will determine the stellar population
(age and metallicity distribution) gradients as a function of the
galactocentric distance. Combined with our previous ground-based study of the
galaxy, this will provide evidences of whether or not Phoenix has a real
``disk/halo'' structure and will allow to trace out the early phases of its
evolution.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8707
Title: A Study of Star Formation in Galactic Resonance Rings
PI: Ronald Buta
PI Institution: University of Alabama

Rings of star formation are a common phenomenon of early-type spiral galaxies.
Most rings form by gas cloud collisions near resonances, under the continuous
action of gravity torques from a bar perturbation, while a small number form
in response to a mild tidal interaction with a nearby companion. In either
case, a resonance is a very special place in any galaxy where star formation
can be enhanced and may proceed either as a starburst or continuously over a
long time period. Resonance rings are natural dynamical laboratories for star
cluster formation and evolution. We are proposing here to study star
formation in two galaxies where we feel certain that the rings are resonance
rings with a different origin. NGC 3081 has four excellent star-forming rings
that are easily connected to bar-driven gas dynamics, while NGC 4622 is a
nonbarred spiral where a strong inner ring is easily connected to a tidal
interaction. We wish to isolate the young clusters in the rings of these two
galaxies, measure their ages and luminosity functions, examine the properties
of the background starlight, and use the information to trace the dynamics of
these galaxies and understand the interplay between perturbations, gas
dynamics, and star formation in normal galaxies.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8708
Title: NGC 625: An Intriguing Nearby Dwarf Starburst Galaxy
PI: Evan Skillman
PI Institution: University of Minnesota

NGC 625 is a dwarf irregular galaxy in the nearby Sculptor group which is
experiencing a strong burst of star formation. Its close proximity and high
galactic latitude make it a very desirable target to help us to understand the
starburst phase of dwarf galaxies. WFPC2 observations are needed to combine
with existing HI synthesis imaging, ground based optical imaging and
spectroscopy, and x-ray imaging in order to construct a coherent model for
this starburst. Specifically, we need high resolution optical imaging at V
and I in order to reconstruct the recent star formation history. This will
allow us to assess the impact of the burst on the HI and the development of
the x-ray emission in a self-consistent way. Our ultimate goal is a better
understanding of the average duration of bursts of star formation and the duty
cycle for bursting star formation in dwarf galaxies through comparative
studies of nearby systems.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8709
Title: UV Light from Old Stellar Populations: A Census of UV
Bright Stars in `Blue Tail' Globular Clusters
PI: Francesco R. Ferraro
PI Institution: Osservatorio Astronomico di Bologna

We propose observations of UV-bright stars in 7 Galactic Globular Clusters
(GGCs). These will complement data obtained during Cycles 5 and 6. Our goals
are multifold: (a) to observe the morphology in the faint blue tails (BTs) of
GGC horizontal branches (HBs); (b) to explore the relationship between the HB
mass distribution in BT clusters to the clusters' structural and dynamical
properties; (c) to gain further samples of Blue Straggler Stars and the long-
sought Cataclysmic Variables in GGC cores; and (d) to obtain relatively large
samples of post main sequence stars. All the targets have a BT which reaches
at least to or beyond the turnoff in V; the actual extent can only be
determined from the uncrowded UV observations. Our observations will allow a
number of studies which cannot be done using ground-based observations: (a)
and (b) will indirectly probe the mass loss process close to the tip of the
red giant branch (RGB), which our data (from previous cycles) suggest to be
often multimodal; (c) provides a complete survey of these peculiar UV stellar
types, along with their radial distributions, will provide fundamental data
for internal cluster dynamics. The observations will add to an archive of
HST\ data on GGC's optimized for the study of hot stellar populations. This
data set, beyond the study of GGCs, will be fundamental to the understanding
of the origin of UV light from elliptical galaxies.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8710
Title: Timing and proper motion measurement of the proposed
optical counterpart of the nearby pulsar PSR1929+10.
PI: Roberto Mignani
PI Institution: ESA Space Telescope European Coordinating Facility

PSR1929+10 is an old (Tau ~ 10^6 yrs), nearby (~ 170 pc) isolated neutron star
detected as an X-ray pulsar. A possible optical counterpart has been detected
by the FOC but the identification still awaits confirmation. Optical
observations of neutron stars include both young (~ 10^3-10^4 yrs) and middle
-aged (~ 10^5 yrs) objects for which different emission models (e.g.
magnetospheric and thermal) have been proposed. However, the general picture
is far from being clear. A firm optical identification of PSR1929+10
would thus be crucial to understand the long term evolution of the optical
luminosity of pulsars and to investigate possible turnovers in the emission
physics. Here we propose to use the STIS NUV-MAMA detector to perform time-
resolved imaging of the proposed counterpart with the double aim of (i)
searching for periodicity at the radio period and (ii) measuring its expected
displacement (~ 500 mas) along the known proper motion direction of the radio
pulsar. A single MAMA observation would thus provide two independent and
complementary proofs to secure the optical identification of PSR1929+10.
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8711
Title: C/O abundance ratios across WCL planetary nebulae with
strong PAH and crystalline silicate emission
PI: Orsola De Marco
PI Institution: Department of Physics and Astronomy - University College
London

ISO has discovered cool O-rich crystalline silicate and water-ice emission in
the far-IR spectra of several planetary nebulae (PNe) which show very strong
hot PAH (polycyclic aromatic hydrocarbon, carbon-rich) emission bands in their
near- and mid-IR spectra. All of these PNe are young and compact and of low-
ionization, and have cool H-deficient Wolf-Rayet central stars. The
correlation with carbon-rich WCL Wolf-Rayet central stars suggests that the
phenomenon is associated with a recent transition from an O-rich to a C-rich
phase by the evolving objects, following the exposure of 3rd dredge-up
enriched material. For these nebulae, the gas-phase C/O ratios (two of the
nebulae have the largest C/O ratios known) are strongly correlated with the
PAH feature strength. The unexpected discovery of cool oxygen-rich particles
around them suggests that strong C/O abundance gradients may be present in the
nebulae. Long-slit spatially resolved STIS spectra will be acquired of three
WCL PNe that simultaneously show PAH and silicate features, in order to test
for C/O spatial variations within them that can diagnose the origin of the two
contradictory chemistries. Only the HST can provide the required high angular
resolution (0arcs1) across these compact (~ 2") nebulae for the crucial
abundance-diagnostic lines of C ii 2326 Angstrom\ and O ii 2470 Angstrom .
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8712
Title: The wind accretion wake in a detached binary system
PI: Thomas Dumm
PI Institution: Swiss Federal Institute of Technology

RW Hya (= HD 117970) is the only known detached binary system, where direct
observational evidence for wind accretion onto a white dwarf is found. STIS UV
observations will enable us to advance our knowledge in a field which has for
long had to remain a theoretical subject. RW Hya is an eclipsing system
containing a mass-losing M-giant and a hot white dwarf on circular orbits (370
days). Close to quadrature, Rayleigh attenuation of the white dwarf UV-
continuum has revealed a strong temporary increase in the column density of
neutral hydrogen in the line of sight. This behaviour is a forceful indication
for an accretion wake trailing the white dwarf. With the proposed STIS/UV
observations of RW Hya, we can for the first time tomographically map the
structure of an accretion wake. The shape of the accretion wake depends on the
properties of the unperturbed M-giant wind as well as on hydrodynamical
processes in the wake. We will therefore be able to study both, M-giant wind
acceleration and dynamics of shocked ionized flows. The proposed set of
spectra will thus yield stringent boundary conditions for refined
hydrodynamical wind accretion simulations in detached binary systems.
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8713
Title: The Photoevaporation of Protostellar Envelopes in the NGC
281 Young Stellar Cluster
PI: S. Thomas Megeath
PI Institution: Harvard Smithsonian Center for Astrophsycis

We propose HAlpha, SII, SIII and R--band WFPC2 imaging of the NGC 281 nebula.
This region, which we have studied intensively at near--infrared and radio
wavelengths, contains a rich cluster of young, low--mass stars emerging from
an edge--on molecular gas/H, ii region interface. With the WFPC2 images, we
plan to search for <= 2000 AU sized evaporating globules, or EGGs, similar to
those detected in M16 by Hester et al. (1996). These globules are thought to
be accreting envelopes surrounding young protostars. By comparing the
proposed WFPC2 imaging with our existing near--infrared (NIR) data, we can
estimate the fraction of stars which emerge from the molecular cloud
enshrouded in EGGs. The goal is to determine whether most stars in the NGC
281 cluster emerge from the clouds still cloaked in their protostellar
envelopes, or whether they disrupt their envelopes prior to emergence. From
this analysis, we will ascertain whether photoevaporation by external OB stars
plays a significant role in terminating protostellar accretion in young
clusters.
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8714
Title: The ^12C/^13C abundance ratio in NGC 3242
PI: Francesco Palla
PI Institution: Osservatorio Astrofisico di Arcetri

We propose to carry out high quality spectroscopic observations of ^12C and
^13C in the ionized gas of the planetary nebula (PN) NGC 3242 by using the C
iii multiplet near <~m 1908 Angstrom. Our goal is to determine the ^12C/^13C
ratio in this object, following the method successfully pionereed by Clegg et
al. (1997). NGC 3242 is the only PN with a measured abundance of ^3He, an
isotope of cosmological interest. The observed ^3He abundance is in agreement
with the predictions of standard stellar evolution models for a ~ 1 M_\odot
star. However, low-mass stars cannot produce ^3He at the level indicated by
NGC 3242 and by standard models otherwise the resulting ^3He abundance in the
Galaxy would be a factor ~ 20--100 higher than observed in the local ISM, in H
ii regions, and in meteorites. The only solution to this problem appears to
rely on a non-standard mixing process that preferentially destroys ^3He during
the RGB/AGB phases. A consequence of such mixing mechanism is the reduction by
a factor ~ 5 of the ^12C/^13C ratio in the stellar envelope. Thus, an
independent measurement of the ^12C/^13C ratio, combined with the available
information on the ^3He abundance, will make possible to perform a crucial
test on theories of low-mass stellar nucleosynthesis. Only STIS on HST can
perform the required UV observations of the C iii multiplet and measure the
carbon isotopic ratio in this unique PN.
================================================================================
Proposal Category: GO
Scientific Category: SF
ID: 8715
Title: A Young Globular Cluster Surrounded by Numerous Smaller
Clusters and a Giant Bubble in NGC 6946
PI: S\oren Larsen
PI Institution: Copenhagen University Observatory

Ground-based images recently lead to the discovery of a young globular cluster
in the nearby spiral galaxy NGC 6946. With an absolute visual magnitude of -
13, this object can be compared to the young globular clusters discovered by
the HST in large numbers in recent merger galaxies like e.g. the Antennae.
However, NGC 6946 is more than a factor of 3 closer than even the most nearby
young merger galaxy, so observations of the young globular here could offer
much more detailed information about the structure and environment of such an
object. The young globular is located within a bubble-like structure with a
radius of about 300 pc, in which dozens of other young clusters are seen on
ground-based images. We have shown in a recent paper that the young globular
could have formed by coalescence of many smaller clusters. Considering the
youth of this region (15 Myr), and its relatively small distance, HST images
are expected to provide detailed information about the formation and early
evolution of globular clusters. This has important implications for
understanding the physical conditions in the early Universe when most globular
clusters and their host galaxies formed.
================================================================================
Proposal Category: GO
Scientific Category: SF
ID: 8716
Title: Search for sub-stellar companions to young brown dwarfs
in the Chamaeleon I dark cloud
PI: Ralph Neuhaeuser
PI Institution: MPI Extraterrestrische Physik

We have discovered 12 very low-mass dwarfs in the Chamaeleon I dark cloud, a
site of on-going star formation, all showing HAlpha emission with spectral
types from M6 to M8. We could obtain medium-resolution spectra for the eight
brightest objects, detected the lithium absorption line, and found the radial
velocity to be consistent with kinematic membership to the Cha I dark cloud.
When placed on an H-R diagram and compared with theoretical evolutionary
tracks and isochrones, we find a range of masses between ~ 0.04 and ~ 0.1
M_\odot and ages from ~ 1 to ~ 10 Myrs. Because the possibly unresolved
systems are already sub-stellar or nearly sub-stellar, any companion would be
clearly sub-stellar, too. We propose to use HST/WFPC2 to observe these young,
very low-mass dwarfs in order to search for close, faint companions. At an
age of a few Myrs, any sub-stellar companion (brown dwarf or giant planet)
should still be relatively bright and self-luminous (powered by on-going
accretion and/or contraction), making its detection much easier than around
older stars in the solar neigborhood. With the exposure times proposed, we can
detect companions down to ~ 5 M_jup at separations as close as ~ 0.3" from the
targets. The detection of young, sub-stellar companions would have important
implication on our understanding of the formation and frequency of planets and
brown dwarfs.
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8717
Title: Observations of Stellar Systems in Seyfert's Sextet
PI: Sally Hunsberger
PI Institution: Lowell Observatory

We propose to obtain imaging in WFPC2 UBVI filters of the compact group of
galaxies known as Seyfert's Sextet, near enough that super star clusters are
detectable and luminosity profiles can be constructed for possible dwarf
galaxy members, yet compact enough that the Sextet can be imaged in one
pointing. Stages of Toomre's merger sequence, from initial encounter through
interaction to final merger, occur simultaneously in the field-of-view. Our
goal is to appraise the epochs of star formation associated with each of these
stages in order to assess the role interactions and mergers play in the
formation of stellar systems (e.g. globular clusters, dwarf galaxies) and in
the evolution of galaxies within dense groups. Analysis of earlier HST
observations (e.g. NGC 4038/9) has shown that stellar population ages can be
determined by imaging in four filters. Single burst star formation systems,
such as super star clusters, will be used to pinpoint eras of starburst.
Stellar ages in tidal dwarfs, i.e., small galaxies forming in tidal tails,
will indicate whether their stars were born in the sudden collapse of an HI
cloud or whether they are clumps of stars torn from the ``parent'' galaxy. The
formation epochs of stellar systems, along with their spatial distribution,
and the detailed morphologies of the giant galaxies will constrain numerical
simulations which attempt to model the Sextet's interaction history and/or the
evolution of compact groups.
================================================================================
Proposal Category: GO
Scientific Category: SP
ID: 8718
Title: Understanding the Anomalous Hot Stellar Population in
Galactic Globular Clusters
PI: Giampaolo Piotto
PI Institution: Universita di Padova

We propose to image in mid- (F255W) and near-UV (F336W) the globular clusters
NGC5986, NGC6273, NGC6388, and NGC6441. During our HST survey we found that
these objects have a horizontal branch (HB) with an anomalously extended blue
tail (EBT) and puzzling gaps along it. The survey F439W and F555W data
indicate that the EBTs of the proposed targets extend up to T_eff>=40000K,
implying that the hottest HB stars have lost almost all their envelope. The
EBTs represent the most extreme of the mixed bag of anomalies known as ``2^
ndparameter problem'', and likely hold the key for understanding the factors
affecting the HB morphology. The UV data, coupled with the existing optical
images, will allow us: 1) to isolate the HB stars from other evolutionary
sequences, enabling the measurement of the fraction of cluster stars in the
EBTs; 2) measure the main physical parameters (as mass and temperature) of the
EBT stars; 3) locate the gaps on the EBTs and measure their statistical
significance 4) to provide tests for the origin of the EBT stars. Also the
blue stragglers (BS) are better isolated in UV, allowing us to check if there
is any relation between the presence of EBTs and the fraction of BS.
Understanding the structure of the EBT stars, and why they are found in some,
but not all systems will help to understand the stellar population of distant
galaxies, and in particular the intringuing UV-upturn phonomenon in
ellipticals.
================================================================================
Proposal Category: SNAP
Scientific Category: COS
ID: 8719
Title: A Continuation of a SNAPSHOT survey of X-ray selected
central cluster galaxies
PI: Alastair Edge
PI Institution: University of Durham

Central cluster galaxies are the most massive stellar systems known and have
been used as standard candles for many decades. Only recently have central
cluster galaxies been recognised to exhibit a wide variety of small scale
(<100 pc) features that can only be reliably detected with HST resolution. The
most intriguing of these are dust lanes which have been detected in many
central cluster galaxies. Dust is not expected to survive long in the hostile
cluster environment unless shielded by the ISM of a disk galaxy or very dense
clouds of cold gas. WFPC2 snapshot images of a representative subset of the
central cluster galaxies from an X-ray selected cluster sample would provide
important constraints on the formation and evolution of dust in cluster cores
that cannot be obtained from ground-based observations. We were awarded 50
SNAPSHOTS in Cycle 8 for this program of which one has been made so far and
another five are scheduled. We wish to continue this project into cycle 9 to
ensure that a sample of more than 50 are observed and cover a number of
recently discovered systems. This project complements our extensive multi-
frequency work on this sample that includes optical spectroscopy and
photometry, VLA and X-ray images for the majority of our targets.
================================================================================
Proposal Category: SNAP
Scientific Category: CS
ID: 8720
Title: Masses and Multiplicity of Nearby Free-floating Methane
and L Dwarfs
PI: Wolfgang Brandner
PI Institution: University of Hawaii, Institute for Astronomy

Brown dwarfs never stabilize themselves on the hydrogen main sequence, so
there is an ambiguity between the temperature or luminosity of a given object
and its mass or age. In order to test the mass-luminosity relations from
(still uncertain) evolutionary models, a direct dynamical determination of
mass is required. As a first step towards a dynamical mass estimate for brown
dwarfs, we have compiled a sample of 50 very-low-mass objects (M<=0.08M_\odot)
in the solar neighborhood (distances 5 pc to 30 pc) with spectral types of L0
and later (including 7 dwarfs with Methane absorption bands in their
atmospheres). Using WFPC2, we propose to observe these objects in two filter
bands with the aim to identify close companions, measure their colors, and to
obtain first epoch data of the newly discovered binaries. We show that the
closest binary brown dwarfs we can resolve will have orbital periods between 3
and 10 yr. Hence, within a few years we should be able to very accurately pin
down masses for brown dwarfs and to calibrate evolutionary tracks. Binary
properties like multiplicity, distribution of binary separations and
brightness ratios hold clues on the origin of free-floating brown dwarf
binaries. Our program will be an important step towards a better understanding
of the still elusive class of brown dwarfs.
================================================================================
Proposal Category: SNAP
Scientific Category: GAL
ID: 8721
Title: A UV Imaging Survey of IR-Bright Star-Forming Galaxies
PI: Daniela Calzetti
PI Institution: Space Telescope Science Institute

We propose to carry out a UV(~1,600 Angstrom) snapshot imaging survey with
STIS of all the actively star-forming galaxies detected by ISO at Lambda>170
Mum and closer than cz=9000 km/s. The sample covers a large region in the
parameter's space of morphology, luminosity, metallicity, and star formation
intensity. The multiwavelength (UV/far-IR) information will be exploited to
address open issues on low- and high-redshift star formation and on the
dust/star-formation interconnection. The ISO galaxies will be used as low-
redshift benchmarks to explore the relationship between the Lyman-break
galaxies at z~3 and the SCUBA sources. The conditions for the escape of UV
light from a `dusty' galaxy will be investigated as a function of the sample
parameters. UV-bright structures will be measured and used to quantify the
fractions of nuclear and disk emission, the fraction of star formation in
massive clusters and the properties of those star clusters, the structural
properties of star forming bars, rings, and tidally-driven star formation in
IR-bright galaxies. Given the breadth of scientific applications and the
relevance of this unique dataset for upcoming instruments and missions,
including mid/far-IR ones like SIRTF, we propose this project as a Service to
the Community and will release immediately the UV images in the public domain.
================================================================================
Proposal Category: SNAP
Scientific Category: HS
ID: 8722
Title: Is Cir X-1 associated with SNR G321.9-0.3?
PI: Roberto Mignani
PI Institution: ESA Space Telescope European Coordinating Facility

Cir X-1 is one of the most intriguing galactic X-ray sources. It is a ~ 16.6
d variable X/radio source, a type I X-ray burster and a QPO emitter, which,
in spite of an ambiguous optical counterpart classification, identify it
as an LMXB. The source is embedded in a radio nebula, with finer structures
protruding towards the centre of the nearby SNR G321.9-0.3. This prompted
the speculation about a connection between the two, with Cir X-1 being
a runaway binary originated from the supernova explosion. In this
case, a a significant proper motion would be expected for Cir X-1. Since
this source has been already imaged by HST in 1992, one more WFPC2 image could
allow to measure its proper motion in the expected direction. This,
together with securing the association with the SNR, will constrain the
age of the neutron star in Cir X-1, crucial to trace its magnetic field
evolution in an accretion regime and to provide observational inputs to
theoretical models. ,bf This is a case where a single, very simple, and short
observation can greatly contribute to solve an important astrophysical issue.
================================================================================
Proposal Category: SNAP
Scientific Category: SP
ID: 8723
Title: A Snapshot Survey of Galactic Globular Clusters
PI: Giampaolo Piotto
PI Institution: Universita di Padova

HST observations of crowded centers of globular clusters (GCs) have produced
intriguing discoveries of new phenomena, most of which are not understood
theoretically. We propose here a continuation of two Cycle 7 and Cycle 8
snapshot proposals, to extend such work to a much larger portion of the
Galactic GC system. Up to now <40\ the Cycle 7--8 targets have been observed,
with results that have been so fruitful that we propose to complete the
original target list, continuing to observe the centers in B and $V with
WPFC2. We request a proprietary period of only 3 months. Our color-magnitude
diagrams will include all stars down to ~ 1^ m below the main-sequence
turnoff, allowing us to address many outstanding questions, such as: How does
the frequency of confirmed or suspected stellar interaction products e.g.,
blue stragglers, horizontal branch (HB) tails depend upon the local stellar
density and the cluster dynamical state? How common are the strange HB
morphologies recently discovered by HST in several GCs, and are they confined
to the central regions? How often do metal-rich GCs have a hot HB, and does
it correlate with the cluster dynamics? We will also improve the core
parameters for a number of GCs, and constrain their dynamical states. This
survey will produce a fundamental data set of Galactic GCs, which will be
useful for a large number of studies in the years to come, and be a part of
the legacy of HST.
================================================================================
Proposal Category: GO
Scientific Category: AGN
ID: 8724
Title: Microarcsecond Imaging of a Gravitationally Lensed QSO:
2237+0305
PI: Rachel Webster
PI Institution: University of Melbourne

The microarcsecond scale structure of the central region of the
gravitationally lensed quasar, 2237+0305, can be determined from its
wavelength dependent lightcurve if viewed during a microlensing event. We are
monitoring the QSO from the ground at regular intervals to ascertain the onset
of a microlensing event. STIS spectra will then be taken and compared with
the spectra taken after the event. As the microlensing event occurs, we will
measure wavelength-dependent changes in the continuum, and also the variations
in lines with different ionizations. Thus we will use microlensing to directly
probe the structure of the source QSO on microarcsecond scales -- a factor of
ten smaller than those revealed by indirect techniques such as reverberation
mapping. An already approved CHANDRA Cycle 1 GO program will provide
complementary x-ray data, thus greatly increasing the wavelength range over
which we hope to probe the quasar's inner structure.
================================================================================
Proposal Category: GO
Scientific Category: GAL
ID: 8725
Title: The Formation Epoch(s) of Globular Clusters Around
Ellipticals from Ultraviolet Photometry
PI: Steve Zepf
PI Institution: Yale University

We propose to study the formation history of elliptical galaxies by obtaining
far-UV photometry of their globular clusters. The far-UV photometry will be
used in conjunction with existing optical data to constrain the ages of these
clusters, and thus the formation epochs of their host galaxies. Optical data
show that globular cluster systems of ellipticals often have bimodal
metallicity distributions, indicating an episodic formation history. However,
the ages of these formation epochs are uncertain. The age distribution is
critical because it directly tests models of the formation of elliptical
galaxies and their globular clusters. Specifically, merger models predict that
the metal-rich clusters are formed in the merger that made the elliptical and
are therefore younger than the metal-poor clusters that come from the halos of
the progenitor spirals. Alternatively, if the observed bimodality comes from
accreting metal-poor clusters onto an already formed elliptical, then the
metal-rich clusters will generally be older. Moreover, age-dating the major
formation epochs of elliptical galaxies provides a critical link between the
local fossil record and the formation history of ellipticals inferred from
deep data. The far-UV to optical color provides this important age information
because the stars that make up the horizontal branch are hotter in older
stellar populations, with significant evolution for otherwise difficult ages
of t > 8 Gyr.
================================================================================
Proposal Category: GO
Scientific Category: ISM
ID: 8726
Title: Cometary Knots in Planetary Nebulae
PI: C.R. O'Dell
PI Institution: Rice University

Cometary Knots trap a significant fraction of all the ejected material in the
closest of the Planetary Nebulae, NGC 7293. This means that these knots may
transport material into free space in a highly preserved state, possibly as
solid bodies, a consequence of some import to understanding the composition of
the interstellar medium. Recent HST and VLT results indicate that the Cometary
Knots are actually quite common among a sampling of nearby Planetary Nebulae,
so that it is likely they are a natural part of the expulsion of material by
intermediate mass stars. We propose second epoch observations of the Cometary
Knots in NGC 7293 in order to get a better idea of just how these objects are
formed by comparison of their spatial motions with that of the ambient gas. We
also propose observations of four Planetary Nebulae that give indications of
the presence of Cometary Knots at different phases of development. These
observational data will be used to quantitatively assess the masses, ubiquity,
and probable survival of Cometary Knots in the sample. Added to our knowledge
of the Cometary Knots in NGC 7293, the set should be large enough to allow
drawing general conclusions about their role in the Planetary Nebula
phenomenon and the interstellar medium.
================================================================================
Proposal Category: GO
Scientific Category: AGN
ID: 8727
Title: Ultra-High Resolution Studies of AGNs III: nuclear extent
and the SIM astrometric grid
PI: Ethan Schreier
PI Institution: Space Telescope Science Institute

We successfully completed a pilot project using the original Fine Guidance
Sensor astrometer (FGS3) to study optical extent of several AGN. We will
extend this work using the significantly enhanced performance of the new FGS
(FGS1R). We will re-observe two high S-N AGN from our earlier sample, probing
the broad line region at 10mas resolution. In an important extension of the
work, we will observe two classes of nearby AGN deemed suitable for the Space
Interferometry Mission (SIM) extragalactic grid. Stable, point-like
extragalactic sources are needed to provide a frame tie from the SIM galactic
grid to a global astrometric reference frame (e.g. ICRF). Because of their
relative brightness, nearby BL Lac & Seyfert 1 objects make up a large
fraction of the flux-limited sample of grid objects. Based on our pilot and
the improved FGS1R performance, we will probe angular sizes of 5-10 mas for
these sources. Resolved structure at these scales would have profound
implications for AGN models. If the nuclear emission remains point-like at the
finer resolution possible with FGS1R, then more stringent limits to the size
of the broad line region and and surrounding emission can be established. Our
program thus has a unique complementarity: resolved structure will be of
general scientific interest, while upper limits to structure will help produce
a reliable input catalog for the SIM astrometric grid.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8728
Title: The Low-Mass Multiple System GL 831 (Wolf 922):
Definitive Orbit and the Mass-Luminosity Relation
PI: Otto Franz
PI Institution: Lowell Observatory

GL 831 = Wolf 922 (V = 11.98, B-V = 1.67, PI = 0.1258 +/- 0.0023 arcsec)
belongs to the select group of about one dozen nearby multiple sytems suitable
for calibrating the empirical mass-luminosity relation for masses below 0.2
Msun\ (Henry et al. 1999), and has been observed 13 times with FGS3 through
Cycle 7. However, a 1.93--yr orbital period, HST scheduling constraints, and a
safe mode event conspired to yield repeated coverage of a 180--deg arc about
apastron, while leaving unobserved the complementary arc containing periastron
(Figure 1). Consequently, the orbital period is accurate to 0.2\ major is
known at best to 1.0\ these orbital elements yield masses with an accuracy
well short of our goal of 5\ Cycle 9 provides the first and only opportunity
in the next three years to complete the coverage by TRANS mode measures needed
to yield a definitive orbit of GL 831 essential for accurate mass
determination. We therefore request five orbits as indicated in Figure 1. New
POS mode data, combined with those in hand, will yield the mass ratio and a
parallax much more accurate than that currently available. Use of FGS1r should
also clarify the location and nature of a fainter third component, possibly of
0.1 Msun, detected in two observations with the less capable FGS3.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8729
Title: Speedy Gonzales Mass Determinations: Fast Orbiting Red
Dwarf Systems
PI: Todd Henry
PI Institution: Johns Hopkins Universtiy

We propose to observe five fast-orbiting red dwarf systems in order to
determine masses for objects near the end of the stellar main sequence. All
five systems have periods of two years or less, hence the moniker ``Speedy
Gonzales'' systems. In addition, all have parallaxes placing them within 10
parsecs, so high quality masses with errors less than 5\ for Cycle 9 is to get
first points on the orbits for three systems (Gl 54, Gl 433, Gl 896) and to
obtain final points for two systems (Gl 791.2 and GJ 2005). For the first
three systems, we will use the data from Cycle 9 to evaluate the best
observing strategies for future Cycles.
================================================================================
Proposal Category: GO
Scientific Category: HS
ID: 8730
Title: The Masses of the O-type Binary 15 Monocerotis
PI: Douglas Gies
PI Institution: Georgia State University

The O-type star 15 Mon (HD 47839) was recently discovered to be an astrometric
and spectroscopic binary with an orbital period of 25 years; it is the first
known O-star system to bridge the observational gap between the period regimes
normally probed by these techniques. An analysis of both the radial velocity
curve and astrometric orbit yields the masses of the components and distance
to the system. Both radial velocity and astrometric measurements are scant at
present, but the system is now close to periastron and continued spectroscopic
and astrometric monitoring will lead to a definitive orbit and yield important
information about the masses of O-type stars. FGS TRANS mode measurements of
separation, position angle, and magnitude difference (begun in Cycle 5) are
needed to bridge the gap between recent speckle observations and anticipated
observations with CHARA Array optical interferometer. In addition, new field
astrometry measurements (FGS POS mode) will provide the proper motion,
parallax, and the binary motion around the center of mass. The POS data will
provide an accurate estimate of the mass ratio and an improved estimate of
distance, and taken together with the spectroscopic and astrometric orbital
data, we should be able to obtain masses for both components accurate to a few
percent.
================================================================================
Proposal Category: SNAP
Scientific Category: SP
ID: 8731
Title: A High Angular Resolution Survey of the Most Massive
Stars in the SMC
PI: Edmund Nelan
PI Institution: Space Telescope Science Institute

To better guarantee the reliability of cosmological calibrations based upon UV
spectroscopy of objects in the SMC, we propose to use HST's Fine Guidance
Sensor (FGS 1R) to conduct high angular resolution observations of some of the
SMC's hottest and most luminous objects. Our plan calls for a comprehensive
survey of nearly every spectral type in the upper portion of the HR diagram.
Binary or multiple star systems will be detected down to an unprecedented
0arcs007 (460 A.U.), more than one order of magnitude better than possible
with WFPC2. The targets we've selected include a representative list of normal
Main Sequence O-stars and their evolved descendents, namely supergiants,
hypergiants, LBVs, and WRs, many of which have been observed by HST's
spectrometers for purposes of cosmological calibrations. The data from these
observations will place much tighter limits on the binary status of these
objects and fundamentally enhance our knowledge of the SMC's upper IMF and
upper stellar mass limit.
================================================================================
Proposal Category: AR
Scientific Category: SS
ID: 8732
Title: Understanding the Physical Structure of the Comet
Shoemaker-Levy 9 Fragments
PI: Terrence Rettig
PI Institution: University of Notre Dame

Images of the fragmented comet Shoemaker--Levy 9 (SL9) as it approached
Jupiter in 1994 provided a unique opportunity to (1) probe the comae, (2)
understand the structure of the 20 cometary objects, and (3) provide limits
on the Jovian impact parameters. The primary cometary questions were: how
were the fragments formed and what was their central structure? There still
remains a diversity of opinion regarding the structure of the 21 comet-like
fragments as well as the specifics of the disruption event itself. We have
shown from Monte Carlo modeling of surface brightness profiles that SL9
fragments had unusual dust size distributions and outflow velocities. Further
work of a preliminary nature showed some of the central reflecting area
excesses derived from surface brightness profile fitting (w/psf) appeared
distributed rather than centrally concentrated as would be expected for comet-
like objects, some central excesses were negative and also, the excesses could
vary with time. With an improved coma subtraction technique we propose to
model each coma surface brightness profile, extract central reflecting areas
or central brightness excesses for the non-star-contaminated WFPC-2 SL9, to
determine the behavior and characteristics of the central excesses as the
fragments approached Jupiter. A second phase of the proposal will be to use
numerical techniques (in conjunction with D. Richardson) to investigate the
various fragment models. This is a difficult modeling process that will allow
us to model the structure and physical characteristics of the fragments and
thus constrain parameters for the Jovian impact events. The results will be
used to constrain the structure of the central fragment cores of SL9 and how
the observed dust comae were produced. The results will provide evidence to
discriminate between the parent nucleus models (i.e., were the fragments solid
objects or swarms of particles?) and provide better constraints on the
atmospheric impact models. The physical characteristics of cometary nuclei
are not well understood and the SL9 data provides an important opportunity to
constrain these parameters.
================================================================================
Proposal Category: AR
Scientific Category: ISM
ID: 8733
Title: Confirming the Interstellar Abundance of Oxygen
PI: Edward Fitzpatrick
PI Institution: Villanova University

The precise determination of interstellar column densities was a major
scientific goal --- and a major success --- of the GHRS. Particularly
important results have been obtained for the element oxygen in the diffuse
ISM. High quality observations and careful analyses suggest that the total
(gas + dust) abundance of oxygen is only 2/3 that found in the Sun. This
result has been interpreted to indicate that the nearby ISM is generally
underabundant in metals compared to the Sun. This has critical bearing on our
view of chemical evolution in the nearby regions of the Galaxy, and also on
the interpretation of other interstellar column density measurements and on
the assumed composition of interstellar dust. As good as the oxygen results
appear to be, they all depend on only one spectral feature, namely, O I
Lambda1355.5977. The generally adopted f-value (i.e., the intrinsic
transition probability) for this line is a theoretical estimate with a quoted
uncertainty of 15\ weight of the oxygen results and interpretation rests on
this single theoretical f-value. I propose to perform an independent
empirical determination of the Lambda1355.5977 f-value using GHRS echelle
observations along 6 sightlines. The results of this program will place the
oxygen analyses on a much firmer footing. The success of this empirical
approach has been demonstrated previously for the Mg II doublet at
LambdaLambda1239, 1240.
================================================================================
Proposal Category: AR
Scientific Category: COS
ID: 8734
Title: Star Formation in E+A Galaxies in Distant Clusters
PI: James Rose
PI Institution: University of North Carolina

It is well-known that star formation occurs at a substantially higher level in
galaxies in distant rich clusters (z>0.3) than it does in their nearby cluster
counterparts. A much-contested issue is what environmental effect leads to
the termination of star formation between z=0.3 and the present epoch. For
instance, there is considerable controversy regarding whether disk star
formation in cluster spirals is simply truncated, perhaps by ram pressure
stripping, or whether the gas is depleted by a major starburst. We propose to
carry out surface photometry of 63 ``E+A'' galaxies in four distant clusters,
and of a similar number of galaxies with ``normal'' spectra, using two-color
WFPC2 imaging of these clusters. The goal is to see whether the E+A galaxies
have bluer nuclei than the surrounding disk, which would indicate the presence
of a recent starburst, as opposed to truncated star formation in the disk. We
have already searched the HST archive of distant cluster images, and located
two-color images of these 63 E+A galaxies. We now request funding to carry
out the surface photometry and color maps, so that we can distinguish between
the two hypotheses for the end of star formation in distant clusters.
================================================================================
Proposal Category: AR
Scientific Category: SP
ID: 8735
Title: Dynamical Correlations for Globular Clusters in the Local
Group Galaxies: Clues About Their Formation
PI: S. George Djorgovski
PI Institution: California Institute of Technology

We propose an archival study of globular clusters in the nearby galaxies M31,
M33, NGC 205, and NGC 185. Our goal is to construct dynamical correlations
for globular clusters in these diverse galaxies and to compare them mutually,
as well as with the properties of the Milky Way globulars. These correlations
probe directly the physics and formative processes of globulars, their
homogeneity (or lack thereof), and can be also used as new distance indicator
relations for their parent galaxies, providing an independent check of other
distance scales. The high angular resolution of the HST images is
emphessential for this project: they will be used to extract a uniform set of
morphological and photometric parameters for these objects, which we will
combine with high-S/N measurements of their velocity dispersions from the Keck
telescope. We would use this data set of fundamental cluster parameters to
perform a detailed dynamical modeling of these systems, including their (M/L)
ratios. We would construct for the first time the Fundamental Plane
correlations for these globular cluster systems, and compare them among the
target galaxies. Perhaps the most interesting is the correlation between the
(M/L) ratios and cluster metallicities. This relation and its scatter probe
directly the cluster IMFs, the dependence of cluster model isochrones on
metallicity, and may even constrain a possible spread in the cluster ages.
================================================================================
Proposal Category: AR
Scientific Category: SP
ID: 8736
Title: The Hydrogen-Burning Limit in the Globular Cluster NGC
6397 (AR part)
PI: Ivan King
PI Institution: University of California, Berkeley

We propose a major enhancement of an earlier study of the bottom of the main
sequence of NGC 6397, the globular cluster with the smallest distance modulus.
In earlier work the lowest part of the MS had been lost among the numerically
dominant field stars; but accurate astrometry, over a baseline of a few years,
now allows an excellent proper-motion separation of faint cluster stars from
the field. The purified CMD follows the main sequence to its ``end" (i.e.,
the terminal plunge of the LF). Just as the MS CMD gives a mass--radius
relation, we show in a new way how this LF can give a mass--luminosity
relation; both of these offer unique checks on theory. Our single WFPC2
field, however, had only a small number of stars in this range, too few to set
firm restraints on the theories. We propose now to increase the number of
such stars by a large factor by (1) getting 2nd-epoch images for three more
fields in the cluster and, (2) in an accompanying AR proposal, remeasuring our
previous images, and others that exist, to the deeper limit that we know can
be attained. The number and the magnitudes of these faintest stars will
greatly strengthen the constraints that we place on structure and atmosphere
theories of lower-main-sequence stars. In each field we will also measure the
anisotropy of internal stellar motions, which is predicted to be large in a
collapsed-core cluster such as this one. as this one.
================================================================================
Proposal Category: AR
Scientific Category: SP
ID: 8737
Title: Geometric Distances of Globular Clusters (AR part)
PI: Ivan King
PI Institution: University of California, Berkeley

This is a proposal to establish a globular-cluster distance scale of
unprecedented accuracy and reliability, with far-reaching impact on the
distance and time scales of cosmology. Our method is to compare internal
dispersions of proper motion with ground-based determinations of the
dispersion of radial velocities. The prospect is a geometrically based
distance scale with an accuracy of better than 2\ ability to make such
measurements, and we are progressing with the conversion of them to a distance
for the cluster. Our project has two parts: (1) Where possible, we use
archival observations for both astrometric epochs (the 2 clusters in the
present proposal). (2) The accompanying GO proposal covers 5 more clusters
for which an archival first epoch exists but we lack second-epoch
observations. With this proposal, the accompanying GO proposal, and other HST
collaborations in which we are involved, we expect to determine accurate
distances for 13 clusters, with a large range of metallicities and second-
parameter characteristics. (Moreover, we intend to cover additional clusters
in future ACS proposals.)
================================================================================
Proposal Category: AR
Scientific Category: SP
ID: 8738
Title: Proper Motions in Well-Observed Fields in Omega Centauri
PI: Ivan King
PI Institution: University of California, Berkeley

The two calibration fields in Omega Cen have been observed repeatedly over the
years, yet have never been exploited scientifically. These two fields are the
main calibration field at 12'\ (5 r_c) and the ``dense'' calibration field at
4arcm6 (2 r_c). The main calibration field, in particular, has been imaged
over 900 times, through a variety of filters. We propose to combine these many
independent observations to obtain exquisite photometry (0.002 mag) and proper
motions (0.07 mas/yr). Our scientific aims are threefold: (1) We will measure
the anisotropy of the velocity distribution. This should be quite large for
this unrelaxed cluster. We will do this as a function of mass, a dynamical
distinction that has never been possible before. (2) We will compare the
internal dispersions of proper motions in these fields with the central
velocity dispersion (as measured in another proposal). Both of these
observations will lead to a new understanding of the dynamics of the cluster.
(3) In the outer field, we will do high-precision photometry of stars along
the main sequence. An earlier study (at 7') showed the main sequence to
bifurcate into two sequences separated in color by 0.05 mags (0.5 dex in
Fe/H). Having photometrically separated the stars into populations of
different metallicity, we can examine the kinematics and spatial distributions
as a function of metallicity.
================================================================================
Proposal Category: AR
Scientific Category: SP
ID: 8739
Title: Absolute Proper Motion of the Fornax Dwarf Spheroidal
PI: Dana Dinescu
PI Institution: University of Virginia

We propose to measure the absolute proper motion of the Fornax dwarf
spheriodal using HST archived images as second-epoch material, and a
combination of Palomar 200-inch and Du Pont 100-inch photographic plates as a
first and intermediate epoch respectively. This project is motivated by the
large number of fields taken with WFPC2 between 1994 and 1999 in the area of
the Fornax dwarf, primarily targeted at Fornax globular clusters. In addition
to these data, the archive contains WFPC2 parallel data as well as a field
with a QSO. For our first epoch we have the plate material that provides an
excellent time baseline (up to 50 years) at a plate scale that allows high-
precision astrometry for relatively crowded fields. We estimate to obtain a
proper-motion error between 0.05 and 0.09 mas yr^-1, a value that depends
primarily on the number of extragalactic objects found on all of the WFPC2
fields, at the limiting magnitude of the plate material (B ~ 22.5). This
proper-motion accuracy will provide tangential velocities of uncertainties
between 30 and 54 km s^-1, which will 1) obtain a dynamical estimate of the
mass of the Galaxy as derived from one of the very distant satellites and, 2)
allow the study of the orbital parameters of the Fornax dwarf and therefore
test its kinematical association with the Fornax-Leo-Sculptor stream proposed
by Lynden-Bell.
================================================================================
Proposal Category: AR
Scientific Category: COS
ID: 8740
Title: Local Cosmology: The Nearby Flow Field and its Structure
PI: Marc Davis
PI Institution: University of California

Our current knowledge of the velocity field of galaxies in the local
neighborhood (<= 500 km/sec) is surprisingly limited. Although tremendous
progress has been made in recent years in mapping the large-scale
gravitational field (out to scales of cz ~ 10,000 km/sec), the major
impediment to constraining the local flow is the lack of a consistent set of
distances to nearby galaxies. Locally the deviations from a pure Hubble
flow have been predicted to be large and measurable, as much as 1 magnitude(
================================================================================
Proposal Category: AR
Scientific Category: COS
ID: 8741
Title: Blending and the Extragalactic Distance Scale: Accurate
DIRECT Distance to M33
PI: Dimitar Sasselov
PI Institution: Harvard-Center for Astrophysics

We propose to use the archival observations by the HST/WFPC2 in an important
galaxy in the cosmological distance ladder, M33, to identify the variable
stars we have already discovered from the ground. The new variables come from
our project, called DIRECT, aiming to obtain the distances to M31 and M33
using detached eclipsing binaries and Cepheids. Combining photometry and
spectroscopy for a selected subsample of binaries and Cepheids allows us to
derive a direct distance of high accuracy, with no intermediate steps. We
expect to identify 25--40\ HST/WFPC2 images, thus improving significantly
their photometry by quantifying systematic effects due to crowding/blending.
We are completing a similar study of M31 (Grant AR-08354.01-97A), which proves
very exciting and successful. It also made us aware of the magnitude of the
task, which requires us to spend an additional year on M33 (summer of 2000).
This should aid in both the accuracy and precision of our direct distance
determination to M31 and M33, which are stepping stones for most of our
current efforts to understand the evolving universe at large scales. Thus we
expect to help in decreasing the HST Key Project's overall uncertainty in
deriving the Hubble constant, H_0, by a factor of 2 (or to about 5\
================================================================================
Proposal Category: AR
Scientific Category: HS
ID: 8742
Title: The Millisecond Pulsars of 47 Tucanae: Mining the Unique
Stellar Equivalent of the Hubble Deep Field
PI: Bruce Margon
PI Institution: University of Washington

Millisecond pulsars (MSPs) in binary systems hold the key to a number of
important problems in astronomy, involving fields as disparate as stellar
evolution, neutron star structure, relativity, and, for those located in
globular clusters, stellar dynamics and cluster structure. Although about a
dozen binary MSPs in the galactic disk now have optical counterparts, and are
thus amenable to detailed study, there are no firm identifications in globular
star clusters, where distances and reddening are accurately known, and the
most interesting dynamical interactions can occur. The optimal cluster to
amend this situation is 47 Tucanae, the cluster with the largest number of
known MSPs, located nearby, and with minimal reddening. By good fortune, in
Cycle 8 an extraordinarily long WFPC2 exposure -- 8 days -- was obtained for
this cluster. Although the motivation for that work was very different than
that discussed here, namely a search for planetary transits, this unique field
is fully the stellar equivalent of the Hubble Deep Field. We propose here to
use newly derived, highly precise radio positions for a large number of MSPs
in 47 Tuc, together with precision astrometric and photometric tools we have
developed in previous HST programs, to greatly increase the number of
optically identified MSPs, and provide the first such identifications in
globular clusters.
================================================================================
Proposal Category: AR
Scientific Category: AGN
ID: 8743
Title: A Morphological and Multicolor HST Survey for Ultrafaint
Quasars, Sampling A Broad Redshift Range
PI: Scott Anderson
PI Institution: University of Washington

Quasars representative of the populous faint end of the luminosity function
are frustratingly dim with m>24 at modest to high redshift; moreover
groundbased surveys for such faint QSOs suffer severe morphological
contamination by compact galaxies. In an initial survey begun several years
ago, we demonstrated the power of combining multicolor photometry with the
0.1'' spatial resolution of HST to yield a morphological and multicolor survey
for quasars to B <=sssim 24. Although limited to z<=sssim 2.1 and based on
only 10 QSO candidates, our initial HST counts both confirmed the severe (>85\
surveys, while simultaneously showing remarkable agreement (albeit with large
errors) with predictions of popular model luminosity functions. These
tantalizing initial results presage the full potential of an HST-based survey
possible now; in the interim many additional WFPC2 fields, observed with more
optimal filter sets, have become available in the archive. Our proposed
program will: (1) increase by 3--8*$ the sample-size of reliable ultrafaint
quasar candidates; (2) broaden the redshift sensitivity to encompass even the
highest-z QSOs; (3) increase the depth surveyed consistently by 3 magnitudes,
extending the logN-logS curve from B~24.5 to B~27.5. This new HST quasar
survey will yield strong constraints on model luminosity functions, even
pending confirming spectroscopy.
================================================================================
Proposal Category: AR
Scientific Category: HS
ID: 8744
Title: Geminga's Parallax Revisited
PI: George Pavlov
PI Institution: The Pennsylvania State University

Measuring distances to neutron stars is extremely important to estimate their
radii, with the aid of temperature determined from X-ray/UV observations. The
first measurement of the distance to a neutron star, based on HST
observations, has been recently reported by Caraveo et al. (1996), who
measured the annual parallax of Geminga, a young, isolated pulsar, active from
the radio to gamma-ray wavelengths. However, that result is based on only
three WFPC2 observations of four now available, and it does not take into
account additional information on the proper motion obtained in recent NICMOS
observations. Moreover, the accuracy of the astrometric analysis can be
improved significantly, making use of more reliable algorithms for centering
point objects in the field and more recent procedures to correct the WFPC2
images for geometric distortion. We propose to use four WFPC2 archival
observations and one NICMOS observation to re-analyze both the proper motion
and parallax of Geminga. The results will have important consequences for the
physics of neutron star interiors, X-ray observations of atmospheres, the
history of Geminga, and the origin of the Local Bubble.
================================================================================
Proposal Category: AR
Scientific Category: SP
ID: 8745
Title: Chemistry of Messier 31
PI: Guy Worthey
PI Institution: Saint Ambrose University

Sampling local group spiral M31 from its nucleus to regions where its halo
fades to nothing, stellar color-magnitude diagrams of the brighter giants will
be used to construct histograms of (fraction of stars) as a function of
(abundance) at each radial location. From these abundance distributions the
following will be derived: (1) the overall radial abundance gradient in the
disk and spheroid of M31 from stars, not nebulae, and (2) the simulated all-
M31 ``closed box'' abundance distribution. These data will be far more
complete and homogeneous than data available for the Milky Way. Chemical
evolution models will be applied to the data. If the observed paucity of metal
-poor stars in the outer disk of M31 continues to the M31 outskirts, it will
be impossible to reconcile any constant-yield model with the M31 data, and, by
inference, spirals in general.
================================================================================
Proposal Category: AR
Scientific Category: COS
ID: 8746
Title: Constraints on the Flattening of Dark Matter Halos from
Galaxy--Galaxy Lensing
PI: Tereasa Brainerd
PI Institution: Boston University

Deep archival imaging data will be used to investigate the degree to which the
dark matter halos of field galaxies deviate from pure spherical symmetry. The
technique that will be used is a measurement of the mean gravitational lensing
shear induced by foreground galaxies in the images of background galaxies, a
phenomenon known as galaxy--galaxy lensing. To date, all investigations of
galaxy--galaxy lensing have focused on a detection of the signal in via a
circular average about the lens center and have implicitly assumed that galaxy
halos are spherically symmetric. However, there is mounting observational
evidence that dark matter halos may be substantially flattened, in which case
their projected surface mass densities will deviate from circular symmetry.
As a result, the gravitational lensing shear pattern that will be induced by
these galaxies will not be circularly symmetric about the lens center. In this
investigation the shear induced by galaxy--galaxy lensing will be computed
along direction vectors defined by the major and minor axes of the images of
the lenses, and the degree to which the shear pattern deviates from circular
symmetry will be quantified. This will be used in conjunction with Monte
Carlo simulations of galaxy--galaxy lensing by flattened halos in order to
place constraints on the overall flattening of the dark matter halos of field
galaxies.
================================================================================
Proposal Category: AR
Scientific Category: COS
ID: 8747
Title: A Broken Rung on the Distance Scale Ladder? - The Case of
NGC 4258
PI: Shoko Sakai
PI Institution: National Optical Astronomy Observatories

Recent determinations of the distance to a spiral galaxy NGC 4258 have sparked
another controversy which could potentially have a significant impact on the
entire extragalactic distance scale. A geometric distance from the
observations of masers in this galaxy yields a distance of 7.2+/- 0.3Mpc
(Herrnstein et al. 1999), while HST/WFPC2 Cepheid observations lead to a
distance of 8.1 +/- 0.4 Mpc (Maoz et al. 1999); the two estimates are
discrepant at the 2Sigma level. If the maser distance, which is independent
of intermediate rungs in the distance scale ladder, is correct, then there
appears to be a need to modify the Cepheid distance scale which has been
serving as the foundation of the extragalactic distance scale. The goal of
this Archival Proposal is to re--analyze the WFPC2 data obtained for the
Cepheid study, and obtain a deep I--band luminosity function from a combined
image, from which the distance will be estimated using the tip of the red
giant branch (TRGB) method. The TRGB method is a Population II distance
indicator, completely independent from the Cepheid distance scale, providing
an independent check on the distance to NGC 4258.
================================================================================
Proposal Category: AR
Scientific Category: AGN
ID: 8748
Title: Testing The AGN/QSO Accretion Disk Paradigm Using New Non
-LTE Models
PI: Matthew Malkan
PI Institution: University of California Los Angeles

We propose to compare a large FOS database of observed quasar spectral energy
distributions to new accretion disk models. We have constructed a large grid
of non-LTE disk models for a wide range of black hole mass and mass accretion
rate, viscosity parameter Alpha, and black hole spins. Our procedure
calculates self-consistently the vertical structure of all disk annuli
together with the radiation field, without any approximations imposed on the
optical thickness of the disk, and without any ad hoc approximations of the
radiation intensity. The total spectrum of a disk is computed by summing the
spectra of the individual annuli, taking into account the general relativistic
transfer function. The results, which include predictions of the polarization
spectrum, differ substantially from previous less reliable models. The FOS
database has sufficient size, spectral resolution, and S/N to allow us to
account statistically for the important effects of intergalactic and
interstellar absorption, as well as the range of expected accretion disk
viewing angles in various AGN subtypes. Our aim is to make a definitive
comparison between observations and accretion disk models.
================================================================================
Proposal Category: AR
Scientific Category: SP
ID: 8749
Title: Comparisons of Local Group Stellar Populations:
Construction of a Public Database
PI: Jon Holtzman
PI Institution: New Mexico State University

We propose to construct a public database of stellar photometry of resolved
stellar populations within Local Group galaxies. We will use this database to
compare stellar population characteristics of different regions in the Local
Group differentially, avoiding some of the complications of comparisons with
stellar evolution models, and to synthesize the results. In particular, we
will address the following issues: beginitemize em What are the relative ages
of the oldest populations in Milky Way neighbors? em To what degree is star
formation is ``bursty'' in different Local Group galaxies? em Is there direct
evidence for variations in the IMF in nearby galaxies? em What is the
``average cosmic star formation history" for dwarf galaxies in the Local
Group? em What is the amount of mechanical and radiative energy input into the
ISMs of different galaxies by massive stars? enditemize
================================================================================
Proposal Category: AR
Scientific Category: GAL
ID: 8750
Title: The Fundamental Plane of Cluster Dwarf Ellipticals
PI: Rafael Guzman
PI Institution: Yale University

We propose to use archival WFPC2 images to measure the structural parameters
(i.e., luminosity profile, half-light radius, surface brightness, and
concentration indices) of dwarf ellipticals (dEs) in the Coma cluster. This
proposal is part of a comprehensive program to study the scaling laws of
cluster dEs. These empirical correlations provide key constrains to models of
galaxy fomation and evolution. Compared to other studies of cluster dEs, this
program is unique in that it includes measurements of the internal kinematics
(i.e., velocity dispersions). Colors, magnitudes, redshifts, line strengths
and velocity dispersions for ~80 dEs in the central 24'*18' region of Coma
have already been measured from deep UBR images and multiobject spectroscopy
using WIYN. In addition to these data, structural parameters are essential to
explore fundamental plane-type correlations. Given the small size of faint
dEs (~0.4'' at Coma), high spatial resolution images are required to measure
their structural parameters. There are 61 archival WFPC2 pointings (mostly in
F606W filter) which provide good signal-to-noise images of ~21 dEs in our
sample. This combined WIYN/HST data set will allow the first determination of
the fundamental plane of cluster dEs, and aims to be a milestone for testing
current theories on the formation and evolution of dwarf galaxies in clusters.
================================================================================
Proposal Category: AR
Scientific Category: SP
ID: 8751
Title: The Age of the Central 100 pc of the Galaxy
PI: R. Michael Rich
PI Institution: University of California at Los Angeles

We propose to compare the age of the Galactic nucleus population with metal
rich globular clusters that are known to be ~ 12 Gyr old. The Galactic
nucleus fields lie behind 10-30 magnitudes of visual extinction, but are now
well imaged to the main sequence turnoff thanks to NICMOS. Preliminary
reductions of fields some 10-20 arcmin from the Galactic Center clearly reveal
a red clump population some 3.5 mag brighter than a clearly detected turnoff.
These reductions suggest that the nucleus, even within 20 pc, is dominated by
an old stellar population. We propose to produce color-magnitude diagrams and
luminosity functions for archival NICMOS images of fields lying 20 arcmin,
1^degrees, 2^degrees, and 3^degrees from the Galactic Center, and to compare
these to the old Galactic globular cluster NGC 6553. The luminosity functions
of the bulge field population and the globular cluster can be directly
compared, independent of distance modulus and reddening, by forcing both to
agree at the maximum of the red clump. This method can give very precise
relative ages of different bulge fields, relative to the oldest stars in the
Galactic halo.
================================================================================
Proposal Category: AR
Scientific Category: COS
ID: 8752
Title: The calibration of the distance scale using Cepheid
Period Luminosity relations at maximum light
PI: Shashi Kanbur
PI Institution: Department of Physics and Astronomy, University of
Massachusetts

This proposal aims to use existing HST Cepheid data to formulate Cepheid
Period Luminosity (PL) relations at maximum light and so recalibrate the
extra-galactic distance scale and estimate Hubble's constant. PL relations at
maximum light are distinct from those at mean light because the physical
conditions in the Cepheid envelope at maximum light are very different to
conditions at all other pulsation phases. In particular, at maximum light the
photospheric temperature is 6200K+/- 200K, independent of period. Current
uncertainties on the distance scale amount to about 0.15 mags or about a seven
percent error in distance. Hence the results of our proposal will be a check
on the existing Cepheid distance scale. Further the use of such maximum light
PL relations may increase the accuracy of the distance scale because the
different envelope conditions at maximum light imply a smaller dispersion at
given period than mean light relations, a flat slope to the period color
relation at maximum light and a way to check reddening determinations. We
will also use the HST Cepheid data to make a detailed comparison of light
curves with their local counterparts to test if they are indeed from the same
population.
================================================================================
Proposal Category: AR
Scientific Category: SS
ID: 8753
Title: Probing the Surface Composition of Europa through
Atmospheric Spectroscopy
PI: Michael Brown
PI Institution: Caltech

We propose to analyze previously obtained spectra of the vicinity of Europa to
search for magnesium in the satellite's atmosphere. Analysis of Galileo NIMS
spectra has led to the suggestion that magnesium is abundant on parts of the
satellite as a hydrated evaporite salt. This interpretation has been
controversial, however, as similar spectra could be produced by mostly pure
water ice under special conditions. In addition, the specific presence of
magnesium is uncertain, as many hydrated salts produce a similar spectrum. Any
salts present on the surface of Europa will be sputtered in the atmosphere
where they are potentially detectable remotely. Our previous groundbased
observations have detected potassium and sodium in the atmosphere of Europa,
which are other possible components of salts on the surface. Detection of
magnesium would be a strong confirmation of the magnesium salt interpretation
of the NIMS data and would help to quantify the trace element composition of
the surface and possibly any subsurface liquid on the satellite.
================================================================================
Proposal Category: AR
Scientific Category: HS
ID: 8754
Title: Probing the Nature of Supernovae through Archival Images
of their Environments
PI: Alex Filippenko
PI Institution: University of California at Berkeley

The locations of supernovae (SNe) in the local stellar and gaseous environment
in galaxies, as measured in high spatial resolution WFPC2 images, contain
important clues to their progenitor stars. They provide accurate
determinations of any association of SNe with H II regions or star clusters.
In cases where multi-filter observations are available, we can determine the
local stellar environment and search for possible attenuation of the SN by
dust in the host galaxy. By checking the fields for background sources, we can
correct the existing SN light curves and luminosities if necessary. When a SN
has been observed incidentally, information can be gained on its optical and
UV emission. Deep HST images can be used to find light echoes of SNe, as well
as recover SNe interacting with circumstellar material at very late times. A
direct search for the progenitor stars of SNe can be made in pre-existing HST
images of their locations. In Cycle 9 we plan to extend our very successful
work from previous cycles. A major improvement is that accurate ground-based
coordinates are now available for numerous SNe. There are images of many host
galaxies in the large and ever-growing HST archive.
================================================================================
Proposal Category: AR
Scientific Category: GAL
ID: 8755
Title: The Radii and Destruction Timescales of Globular Clusters
in NGC 3610
PI: Steve Zepf
PI Institution: Yale University

The luminosity function of well-studied old globular cluster systems is log-
normal, while that of candidate young globular cluster systems is a power-law.
If some of the young clusters are to be identified as globular clusters, the
luminosity function must evolve to become log-normal. Several recent
theoretical calculations find that dynamical evolution naturally changes a
power-law mass and luminosity function into a log-normal one through the
preferential destruction of low-mass clusters. However, there is no
observational evidence for evolution of cluster luminosity functions. We
propose to use archival WFPC2 images of NGC 3610 to study the luminosity
function of its globular cluster system, which has been recognized as having a
significant intermediate age component. We will test whether the cluster
luminosity function in NGC 3610 is intermediate between M87 (a quiescent
elliptical) and NGC 3256 (an ongoing merger) as expected from dynamical
models. Moreover, we will determine the radii of the NGC 3610 globular
clusters using King model fits, applying techniques we have developed in our
study of other cluster systems. The radii determined this way will provide
much better input into the models of dynamical destruction of globular
clusters, and therefore into model predictions for the location of a turnover
in the globular cluster luminosity in the intermediate aged NGC 3610 system.
================================================================================
Proposal Category: AR
Scientific Category: GAL
ID: 8756
Title: A Search for Extremely Red Objects Using Archival WFPC2
Images
PI: Lin Yan
PI Institution: The Observatories of Carnegie Institute of Washington

To date HST/WFPC2 has imaged over 450 fields at intermediate and high galactic
latitudes to a depth of I_c ~ 26 mag (3Sigma in an 1Box^'' aperture) in the
F814W filter. We propose an archival research program using these deep images
in combination with ground-based K-band observations, to search for extremely
red objects (EROs) with I_c - K > 5 and K < 19.0. We will survey roughly 1700
square arcminutes and expect to detect 68 bright EROs. The HST archive offers
us two unique advantages to carry out an efficient survey: it provides a
wealth of deep I-band images otherwise difficult to obtain from the ground,
and the high resolution images will enable us to study in detail the
distribution of ERO morphological types as a function of color. With the
advent of large format near-IR detectors, imaging bright EROs in K-band over a
large area is becoming efficient. In two years, this survey will produce the
largest sample of bright EROs, useful for follow-up studies to determine the
nature of EROs. Our ultimate goals are to 1). measure the percentages of old
elliptical and dusty starburst galaxies among the overall ERO population,
setting strong constraints on theories of the formation and evolution of
massive galaxies; 2). determine how significant the starburst EROs contribute
to the global star formation rate; and 3). determine the relationship between
EROs and the local ultra-luminous IRAS galaxies.
================================================================================
Proposal Category: AR
Scientific Category: HS
ID: 8757
Title: Systematic Serendipitous Discovery of Cataclysmic
Variables and Other Odd Stars in Globular Clusters
PI: Eric Deutsch
PI Institution: University of Washington

Despite indications that classical cataclysmic variable (CV) stars are rare in
globular clusters in general, and in the cluster NGC 6624 in particular, we
have serendipitously discovered such a star ~6'' from the cluster center. An
HST STIS spectrum of the m~22 object, which fell accidentally in the slit
during an unrelated program, shows strong, broad emission lines typical of
numerous field CVs, and the inferred optical and UV luminosity are also
similar. That we have detected such an object in an observation that includes
just a few percent of the central area of the cluster may indicate that
cluster CVs are more common than previously thought. Here we propose a very
simple archival program to examine all public STIS near- and far-UV spectra in
globular clusters for similar objects, as well as other unusual hot stars.
================================================================================
Proposal Category: AR
Scientific Category: GAL
ID: 8758
Title: Morphology of Butcher-Oemler Galaxies
PI: James Schombert
PI Institution: University of Oregon

This archival proposal is to analyze WFPC2 and NICMOS images of distant
clusters, which have complimentary ground-based narrow band photometry, to
investigate the Butcher-Oemler effect. Our narrow band work has isolated a
population of faint starburst galaxies in Butcher-Oemler clusters which may
provide insight into the debate between the galaxy harassment models and gas
supply proposals for the star formation behavior behind the Butcher-Oemler
effect. The primary goal of this project is to determine the basic
morphological and structural properties (scale lengths, surface brightness,
bulge-to-disk luminosities) of the blue population in clusters and, in
particular, to determine what kind of galaxy is involved in ordinary star
formation versus a starburst phenomenon as assigned by narrow band colors. A
newly discovered low luminosity starburst population will be studied to test
whether they are future dwarf galaxies.
================================================================================
Proposal Category: AR
Scientific Category: GAL
ID: 8759
Title: Kinematics of nuclear stellar disks around massive
central black holes
PI: Monica Valluri
PI Institution: Univerisity of Chicago

HST imaging has revealed the presence of nuclear stellar disks at the centers
of several early-type galaxies. Simultaneously, spectroscopic studies of
galactic nuclei have yielded dynamical evidence for supermassive black holes
with masses of 10^6 - 10^9Msun in about a dozen galaxies. Not an
insignifcant fraction of the quiescent black holes appear to be associated
with comparably-massive (~10^8Msun) stellar disks. The kinematics of these
disks provide the most direct route to determining the masses of the black
holes. They may also provide vital clues to the formation of black holes and
establish a more tangible link to the quasar epoch: nuclear stellar disks may
be remnants of more massive gas disks that fuelled the black holes in quasars.
We propose to use archival STIS data obtained for the study of ``demographics
of nuclear black holes'' to carry out a search and analysis of nuclear stellar
disks in 7 galaxies. This study will allow us to determine the dynamical
masses and other properties of disks (where present) and will also help to put
tighter constraints on the masses of central black holes.
================================================================================
Proposal Category: AR
Scientific Category: SS
ID: 8760
Title: The Dynamics of Dark Spots on Neptune
PI: Lawrence Sromovsky
PI Institution: University of Wisconsin-Madison

HST and groundbased observations of Neptune since 1991 provide potentially
strong constraints on the behavior of Neptune's Northern Great Dark Spot
(NGDS), first discovered in October 1994 HST images (Hammel et al., Science
268, 1995). Unlike the 1989 Great Dark Spot revealed by Voyager, which moved
continuously equatorward and dissipated unseen during 1990, the NGDS seems to
have remained at ~ 35degrees N from 1994 through at least 1996, suggesting
that its zonal drift rate may be relatively constant and that its position may
be highly predictable. An empirical model of its motion can be constrained by
analysis of HST archive images in combination with existing groundbased images
that are sensitive to the bright companion clouds of the NGDS. By combining
sporadic groundbased observations of the companion clouds during 1993, 1994,
1996, 1997, and 1998, with HST observations of both the NGDS and its bright
companion in 1994, 1995, and 1996, and HST observations of only bright
companions in 1991, 1997, and 1998, we propose to determine spectral and other
signatures for the companion clouds, the evolution of their characteristics,
and whether or not the NGDS is a single circulation feature that has been
present during this entire period. We expect to provide new constraints on
NGDS dynamics and companion lifetimes and a prediction equation for NGDS
future positions.
================================================================================
Proposal Category: AR
Scientific Category: SS
ID: 8761
Title: Inclined Features in Saturn's Rings
PI: Amanda Bosh
PI Institution: Lowell Observatory

The occultation of GSC529-01240 observed in 1995 with the FOS on HST (GO-5824,
Bosh PI) was the most sensitive occultation to date for inclinations in
Saturn's rings. The F ring has been determined to be inclined using these
data, and this has been independently verified with WFPC2 imaging of the F
ring entering eclipse (possible only for an inclined F ring). Additional ring
features in this data set exhibit signs of possible inclination (high radial
residuals in just the 1995 data set). We propose to investigate these ring
features for inclinations using the same method as was applied to the F ring.
The improved kinematic models that will result from these analyses will lead
to better understanding of narrow ringlet confinement. The determination of
Saturn's gravitational harmonics and thus its interior structure will also be
improved due to better ringlet models, as several ringlets are now used as
significant constraints to these parameters.
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Proposal Category: AR
Scientific Category: COS
ID: 8762
Title: The Fundamental Plane of Cluster Ellipticals at z = 0.18:
Establishing the Local Baseline
PI: S. George Djorgovski
PI Institution: California Institute of Technology

The process of assembling of galaxies into rich clusters may leave distinctive
signatures in the stellar populations and morphological mix that depend on
position in the cluster, and evolve with redshift. We propose to study the
properties of galaxies in the core and halo of the galaxy cluster A1689 at z =
0.18 using a combination of HST optical, emphmosaic imaging (archival), ground
-based optical and IR imaging (already obtained), and Keck medium resolution
spectroscopy. This study will alleviate systematic uncertainties in the very
local studies of the cluster galaxy population (in Coma) and form a bridge to
the results from intermediate- to high-z systems. As a function of local
galaxy density within each cluster, we will study the projections of the
Fundamental Plane correlations (the optical-infrared color-magnitude relation
and the radius-luminosity relation), the IR luminosity function, and the
changing morphological mix. Keck spectroscopy will play a vital role in
efficiently determining velocities and rotation curves for cluster members.
The images will also be searched for extremely-red galaxies---which could
represent high-redshift elliptical (z ~ 1) or star-forming (z > 4) galaxies
lensed by the rich clusters. emphThis study is unique in that both the ground
-based IR imaging and the HST optical imaging mosaic a wide-field, thereby
allowing for the simultaneous study of galaxies in the core and the halo of
the cluster.
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Proposal Category: AR
Scientific Category: AGN
ID: 8763
Title: The Cause of Narrow Absorption Lines Intrinsic to Quasi--
Stellar Objects
PI: Jane C. Charlton
PI Institution: The Pennsylvania State University

We propose to investigate the archived FOS (R=1300) observations of quasars
for the purpose of understanding the origins of low redshift (z<1) associated
(Delta v<5000 kms) CIV narrow absorption lines (NALs). Many of these NALs are
intrinsic to the quasar and are likely to be related to outflow or inflow from
the central engine. Therefore, their rate of incidence and its relationship
to other quasar properties will constrain the geometry, ionization conditions,
and kinematics of these flows. From studies of high redshift quasars, the
existence of intrinsic NALs is likely to require some complex combination of
QSO properties, and results from ground--based work in this area have left
many questions as yet unanswered. Are NALS the result of orientation relative
to the line of sight? Is it related to the relative (to Eddington) luminosity
of the accretion disk? Only at low redshift, with data from the HST/FOS
archive, can we study quasars with a range of luminosities, and accurately
determine their radio morphologies and X--ray properties. Employing radio and
X--ray data (luminosity, spectral index, morphology) from both the literature
and online catalogs (e.g. NVSS, RASS), we will perform multivariate and 2--
sample statistical tests to determine the combination of QSO properties that
give rise to the presence of NALs along the line--of--sight.
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Proposal Category: AR
Scientific Category: GAL
ID: 8764
Title: Archival Search for a White Dwarf Dark Matter Component
via WFPC2 Proper Motion Measurements
PI: Arlin Crotts
PI Institution: Columbia University

We propose searching for proper motions of faint blue objects in a previously
well sampled field. Such objects have been recently detected in the HDF and
are suggested to be old halo white dwarfs (Ibata et al. 1999). If this
identification is correct, and the implied density persists, a major portion
of the dark matter in galactic halos will have been found. A dominant baryonic
component in dark halos has dramatic consequences for fields spanning much of
astronomy and astrophysics. Theories of structure and galactic formation would
have to be revised, while our understanding of stellar birth would need to
account to the drastically different IMF required to produce halo white
dwarfs. In addition the baryon and metallicity budgets of the universe would
be profoundly effected. With the addition of the previously analysed HDF, our
selection of a field at high galactic latitude would also allow us to begin
examining the spatial distribution of the new population. A true halo
population should be clearly distinguishable from a thick disk-type
distribution via the directions and magnitudes of the proper motions as a
function of (l,b). Since these objects are faint (V ~ 28.5) and require high
precision astrometry only HST can study them. We choose the best archival
field to evaluate this approach, with no additional cost in HST time.
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Proposal Category: AR
Scientific Category: GAL
ID: 8765
Title: An Archival Study of The Mid-UV Structure of Nearby Early
-Type Galaxies
PI: Claudia-Angelica Chiarenza Burg
PI Institution: Arizona State University

Currently, very little is known about nearby galaxy morphology in the UV. The
restframe wavelength of galaxies at z~1 observed by HST in the R band is
3000\A. Therefore, before we can fully understand the morphology of the many
irregular galaxies that we see at high redshifts, we must first understand
what nearby galaxies look like in the UV. Images below 3100\A cannot be
obtained from ground-based telescopes due to the earth's atmospheric cutoff.
We propose to use Archival WFPC2 images of nearby galaxies in F300W, plus
ground-based UBVR, to study morphology as a function of wavelength. The
2930\A filter on HST extends from ~2500\A-3200\A (half power points), thus
extending much further into the UV than ground-based U(360). This proposal
will look at the predominantly early to mid-type galaxies found in the (F300W)
Archive. We also propose to search the Archive F300W images taken in parallel
mode for the few 'chance' nearby galaxies contained in them. Specifically, we
will use the targeted and parallel F300W images in the Archive, along with our
ground-based data to address the following issues: o morphology as a function
of Hubble type and restframe wavelength for early and mid-type galaxies in the
mid-UV o apply proper bandpass shifting effects to get more reliable distant
galaxy classifications
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Proposal Category: AR
Scientific Category: COS
ID: 8766
Title: Color Gradients in Elliptical Galaxies at z = 0.5: , An
Indicator of Galaxy Formation Processes
PI: Michael Pahre
PI Institution: Smithsonian Astrophysical Observatory

We propose to make a direct comparison of the frequency and size of color
gradients in cluster elliptical galaxies at z ~ 0 and z ~ 0.5 to constrain the
relative roles of merging and monolithic collapse on the galaxy formation
process. Color gradients are ubiquitous in elliptical galaxies in the local
universe, and are the origin of 20-50\ Local studies of color (and line-
strength) gradients could be explained by metallicity and/or age gradients in
the underlying stellar populations, but offer few clues as to how they could
have formed. HST observations at z ~ 0.5, however, can provide direct
insight into the origin(s) of these population gradients: the gradients
steepen with redshift if dissipationless merging dominates; flatten if
dissipative, gas-rich merging dominates; or remain roughly constant if
monolithic collapse (at early epochs) created the population gradients. In
order to test these predictions, we will utilize both ground-based and HST
data: ground-based observations in (U-V) at z~ 0 are a nearly exact match in
color and physical resolution to HST archival observations in (555-814) of
three clusters at z ~ 0.5. Color gradients are shown to be easily measured
with HST at z ~ 0.5, but they have yet to be studied in a systematic manner.
Funding is requested here primarily to support a Harvard undergraduate to
reduce, analyze, and publish the results of the study.
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Proposal Category: AR
Scientific Category: COS
ID: 8767
Title: Evolution of 1200 Field E/S0 Galaxies to z = 1
PI: Myungshin Im
PI Institution: University of California Observatories/Lick Observatory

The evolution of field E/S0 galaxies, especially their number density, is in
debate. Theoretical models based on hierarchical structure formation predict
that a significant fraction of present day E/S0's are formed at z < 1 via
merging. This is in sharp contrast to the so-called ``monolithic collapse''
model which predicts the coeval formation of E/S0's at high redshift (z >> 1).
Current observational constraints on the evolution of field E/S0's are
controversial, mainly because of the lack of a sample large enough to provide
statistically significant limits. From the HST Archive, we have identified
230 WFPC2 fields at high Galactic latitude which have V and I imaging of
sufficient depth for morphological identification of E/S0's to I = 22. In
these fields, we estimate that there will be ~ 1200-1400 normal, luminous,
field E/S0's with I < 22, z < 1 and z_med ~ 0.5, enough to provide significant
improvement in the number statistics over previous studies. This large sample
of E/S0 galaxies will constrain : i) the number density evolution of field
E/S0's at z < 1 to an accuracy of better than 10\ ii) the luminosity evolution
of field E/S0's since z=1; and iii) the cosmological parameters. Knowing the
number density should settle whether merging since z=1 can have been a major
process in the formation of E/S0's.
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Proposal Category: GO
Scientific Category: GAL
ID: 8769
Title: The red giant stellar population in three nearby low-
metallicity blue compact dwarf galaxies
PI: Trinh Xuan Thuan
PI Institution: Astronomy Department, University of Virginia

We wish to obtain deep V and I WFPC2 images of three nearby metal-deficient
blue compact dwarf (BCD) galaxies I Zw 18 (Z_\odot/50), UGC 4483 (Z_\odot/23)
and NGC 2366 \equiv Mrk 71 (Z_\odot/13). Our main goal is to detect the red
giant stellar population in these resolved BCDs to study their evolutionary
history and constrain their ages. Are they young or old? On the basis of
chemical evolution arguments, we have argued that all galaxies with Z <
Z_\odot/20 are young with ages < 100 Myr, while those with Z > Z_\odot/20 are
older. The high spatial resolution of the WFPC2 will allow to detect stars ~ 3
mag fainter than the red giant tip in UGC 4483 and NGC 2366, both members of
the M81 group at a distance of 3.44 Mpc, and determine stellar ages directly
through color-magnitude diagrams. If our chemical evolution arguments are
correct, then UGC 4483 should not possess a red giant population and not be
older than ~ 100 Myr, while such a population should be present in NGC 2366.
As for I Zw 18, we shall concentrate on its C component where crowding is
less than in the main body. If I Zw 18 is at the commonly assumed distance of
10 Mpc, then we should be able to detect the brightest red giant stars if they
are present. In that case, the age of I Zw 18 would be greater than ~ 1 Gyr.
Conversely, if red giant stars are absent, then either I Zw 18 is young (<=
100 Myr) or it is further away (D > 15 Mpc) than commonly assumed.
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Proposal Category: AR
Scientific Category: AGN
ID: 8768
Title: The Morphological Mix of Faint Radio Sources From
Archival WFPC2 Images

PI: Ian Waddington
PI Institution: Arizona State University, Dept of Physics & Astronomy

We propose to investigate the optical morphologies of ~ 300 faint
radio sources using archival HST\ images. Using the FIRST survey and
several deep VLA fields, we will assemble a sample of radio sour ces
spanning five orders of magnitude in radio flux from 10^-5 Jy to 1 Jy
at 1.4 GHz, that have WFPC 2 F606W/F814W images available in the
archive. We will then use this sample to achieve the followin g
goals: hbox(square)uare Determine the radio source counts as a
function of optical morphology a nd radio flux density, allowing us to
differentiate the various galaxy types that make up the faint radio
source population. hbox(square)uare Determine the fraction of faint
radio sources that have no optical counterpart to I~eq 25--27. Such
objects must either be heavily obscured by dust, or be at very high
redshift, or be high-redshift dusty sources. We previously found
several such objects in the HDF-N. hbox(square)uare Determine the
extent to which weak radio galaxies have their optic al emission
aligned with their radio axis, as is typical of powerful radio
galaxies at z>~ 0.6. hb ox(square)uare Investigate the environments
of faint radio sources. The radio emission from microja nsky sources
is attributed to high star formation rates in these galaxies --- we
will be able to det ermine what fraction of these starbursts are
caused by interactions or mergers.
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Proposal Category: GO
Scientific Category: CS
ID: 8770
Title: The Nucleosynthesis of Boron - Benchmarks for the
Galactic Disk
PI: Ann M. Boesgaard
PI Institution: Institute for Astronomy, University of Hawaii

In spite of several HST cycles of boron abundance determinations, we do not
know the true, ambient, present-day abundance of B. Only two stars (with
undepleted Li and Be) have been observed to derive the Population I true B
abundance. Past cycles have focused on (1) halo stars with low metallicity
and (2) solar-type stars with Li and/or Be deficiencies. In this study we
wish to determine stellar abundances of boron, measured from the B, i
2497Angstrom\ line from STIS echelle spectra, of main sequence F-G stars that
have retained their full initial abundances of boron. Our target stars are
those for which ground-based observations show that beryllium is undepleted.
These new abundances will map evolution of the boron abundance in the Galactic
disk in the metallicity range from one-third solar up to solar. Then the B,
and previously determined Li and Be abundances, will be used to improve
understanding of the nucleosynthesis of B. In particular, we will be able to
assess the relative contributions from cosmic ray-induced spallation vs
neutrino-induced spallation in Type II SN, that are predicted to synthesize B
(as ^11B) but not Be. Since the former process is the only identified site of
Be synthesis, the B/Be ratio can be used to resolve the contributions of
neutrino and cosmic ray induced spallation.
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