Cycle 13 Abstract Catalog
Generated on: Wed Apr 14 10:07:54 EDT 2004

================================================================================

Proposal Category:   GO
Scientific Category: COOL STARS
ID:                  10114
Title:               Lyman_alpha FUV observations of the Sun in time and
                     effects on planetary atmospheres
PI:                  Edward Guinan
PI Institution:      Villanova University

The chromospheric H I Ly_alpha 1215.6 feature is the dominant source of short-
wave emission in the Sun and solar-type stars, contributing about 80-90% of
the total FUV flux and 30-60% of the total flux between 1 and 1500 A. Also,
this important chromospheric line is the major cooling channel for cool star
atmospheres. Accurate Ly_alpha fluxes are the only missing element of our
ongoing "Sun in Time" program. This program studies a sample of single G0-5 V
stars with well-known physical properties that serve as proxies for the Sun
(and solar-mass stars) over their main sequence lifetimes. One of the major
goals of the program is the determination of the spectral irradiance of the
early Sun. Our analyses indicate that the strong XUV emissions of the young
Sun have played a crucial role in the developing planetary system. In
particular, the expected strong Ly_alpha line flux may have greatly influenced
the photoionization, photochemical evolution and possible erosion of planetary
atmospheres, as well as played a role in the origin and development of life on
Earth. The "Sun in Time" data can also be applied to investigate the
atmospheric loss of exoplanets around solar-type stars resulting from XUV
heating, which can eventually lead to the evaporation of "hot Jupiters". We
propose to use HST/STIS-MAMA/E140M to determine accurate FUV and Ly-alpha
fluxes and irradiances for 4 representative solar proxies with ages from 130
Myr to 6.7 Gyr. It is only with HST's high-resolution UV spectroscopy (to
correct for ISM absorption) and the small aperture (to eliminate geocoronal
emission) that the stellar Ly-alpha profile can be reliably modeled and its
flux measured. The proposed study is of capital importance in reconstructing
the evolutionary histories of exoplanets already known and additional planets
that missions such as COROT, Kepler, SIM, and Darwin/TPF will discover in the
coming years.
================================================================================

Proposal Category:   GO
Scientific Category: SOLAR SYSTEM
ID:                  10115
Title:               Rotation of Comet Tempel 1
PI:                  Michael A'Hearn
PI Institution:      University of Maryland

We propose to accurately determine the rotational period of comet Tempel 1.
This is crucial for enabling all of the science associated with the Deep
Impact mission.  It will also, in combination with ground-based data already
on hand and images to be obtained from Deep Impact, provide the best dataset
ever for investigating whether excited state rotation exists in any comet
other than Halley.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10116
Title:               Towards an Accurate Calibration of the Galactic Cepheid
                     P-L Zero Point
PI:                  Edward Guinan
PI Institution:      Villanova University

The young open cluster NGC 7790 is unique and astrophysically important
because it contains three classical Cepheid variables (CF Cas, CE Cas A, and
CE Cas B). If the distance of NGC 7790 were known with certainty, these
Cepheids would define the zero point for the galactic Cepheid Period-
Luminosity (P-L) relationship. By a stroke of good luck, NGC 7790 also
contains a 10th-mag eclipsing binary located near the turnoff of the main-
sequence of the color-magnitude diagram of the cluster. This important
eclipsing binary has been little studied until now and contains two B1IV-V+B3V
stars with an orbital period of P=6.005 days. With HST we propose to secure
the accurate distance and reddening of QX Cas (and thus of the Cepheids) by
using eclipsing binaries as precise standard candles, as we have demonstrated
in our work on the Large Magellanic Cloud. With absolute radii, temperatures,
and luminosities of the stars known from ground-based and HST observations,
the method is essentially geometric and free from many of the uncertainties
that plague other less direct methods. Light and radial velocity curve data
will be combined with the proposed HST/STIS spectrophotometry (1150-8000 A) to
determine the physical properties of the eclipsing binary and thus to secure
an accurate distance and reddening for NGC 7790. The determination of the
stars' temperatures, reddenings and chemical abundances, and therefore the
cluster's distance, with the necessary accuracy can only be accomplished with
HST. According to our previous experience, we expect a resulting distance
determination with an accuracy of about 2-3%. HST/STIS spectrophotometry will
be carried out also for the three Cepheids to determine their properties and
individual reddenings. Thus, the proposed HST observations could help
eliminate the current nagging uncertainty of the galactic Cepheid zero point
and provide the key for a firm calibration of the P-L relationship.
================================================================================

Proposal Category:   SNAP
Scientific Category: AGN/QUASARS
ID:                  10117
Title:               The Co-Evolution of Star Formation and Powerful Radio
                     Activity in Galaxies
PI:                  Christopher O'Dea
PI Institution:      Space Telescope Science Institute

We will carry out a STIS/NUV-MAMA snapshot imaging survey of the most compact
powerful radio galaxies, the Gigahertz Peaked Spectrum (GPS) sources and
Compact Steep Spectrum (CSS) sources.  These objects are as powerful as the
large radio doubles but are much smaller (and younger) and are crucial to our
understanding not only of how radio-loud active galactic nuclei (AGN) form and
evolve, but also what role they play in the evolution of galaxies. A very
direct and robust way to address these issues is by high resolution  imaging
of the host galaxies of these sources in the UV. This has never been done
before for a sample of these very compact sources, since previous HST/UV
imaging programs have focussed on the larger radio galaxies. The UV emission
can provide crucial information about any recent star formation that may have
occurred as a result of ongoing accretion, mergers, interactions, or
triggering by the radio source. By comparing the starburst properties of GPS,
CSS, and large scale radio sources, we will be able to constrain the evolution
of massive star formation as a function of the relative age of the radio
source.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10118
Title:               Imaging the Chemical Distribution in Type Ia SN Ejecta
PI:                  Robert Fesen
PI Institution:      Dartmouth College

We know Type Ia supernovae are thermonuclear explosions of CO white dwarfs,
but we don't know the specifics of how the nuclear burning process proceeds
from the core outward once it starts. The thermonuclear instability is thought
to start off as a subsonic, turbulent deflagration or burning wave but then,
at some point, may transition into a blast or detonation wave. In such
"delayed detonation" models, differences between normal and subluminous Type
Ia SNe reflect differences in the amount of burning that has occurred in the
pre-detonation phase. More burning helps to pre-expand the WD before passage
of the detontation wave, which then results in different final element
abundances and internal Fe-rich ejecta structure.  Directly imaging the 2-D
chemical distribution of ejecta from a Type Ia SN is actually possible in the
case of the subluminous Type Ia SN 1885, which occurred on the near-side of
M31's central bulge.  This 119 year old remnant is visible -- from its core to
its outer edge -- via strong optical/UV Ca and Fe line absorptions.
Remarkably, the SNR appears to still be in a nearly free expansion phase,
meaning that the elemental stratification seen present today accurately
reflects SN Ia explosive nucleosynthesis physics.  We propose to obtain ACS
WFC/HRC images of SN 1885 in order to take advantage of this extraordinary
situation: Having a young, nearby Type Ia SN remnant visible in silhouette
against a galaxy-size light table. These unique observations will reveal a SN
Ia's Ca and Fe ejecta distribution, density structure, sphericity, and
ionization state as a function of expansion velocity, thereby confronting
various SN Ia models with detailed ejecta stratification and expansion
velocity maps.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10119
Title:               Solving the Mystery of the Short-Hard Gamma-Ray Bursts
PI:                  Derek Fox
PI Institution:      California Institute of Technology

Seven years after the afterglow detections that revolutionized studies of the
long-soft gamma-ray bursts, not even one afterglow of a short-hard GRB has
been seen, and the nature of these events has become one of the most important
problems in GRB research.  The forthcoming Swift satellite will report few-
arcsecond localizations for short-hard bursts in minutes, however, enabling
prompt, deep optical afterglow searches for the first time.  Discovery and
observation of the first short-hard optical afterglows will answer most of the
critical questions about these events: What are their distances and energies?
Do they occur in distant galaxies, and if so, in which regions of those
galaxies?  Are they the result of collimated or quasi-spherical explosions?
In combination with an extensive rapid-response ground-based campaign, we
propose to make the critical high-sensitivity HST TOO observations that will
allow us to answer these questions.  If theorists are correct in attributing
the short-hard bursts to binary neutron star coalescence events, then the
short-hard bursts are signposts to the primary targeted source population for
ground-based gravitational-wave detectors, and short-hard burst studies will
have a vital role to play in guiding their observations.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10120
Title:               The Formation Histories and Dynamical Roles of X-ray
                     Binaries in Globular Clusters
PI:                  Scott Anderson
PI Institution:      University of Washington

Close binaries are fundamental to the dynamical stability and evolution of
globular clusters, but large populations have been extremely difficult to
identify. Chandra X-ray images provide a revolutionary resource, revealing a
few to dozens of low-luminosity X-ray sources in every cluster deeply
examined; our own Chandra programs uniformly study these ubiquitous X-ray
sources (close binaries and their progeny) in 11 clusters. However, definitive
understanding of the nature of the various X-ray subpopulations requires the
identification of optical counterparts, and HST is the demonstrated key in
these crowded environments. We thus propose a proven, efficient, and uniform,
HST multicolor imaging program for optical identifications in 6 of our
clusters with Chandra data on-hand, but which lack adequate optical images in
the HST archive. The proposed ACS images will permit statistical
classifications into the various subtypes: CVs, qLMXBs, BY Dra's/RS CVn's (and
MSPs). A unique aspect of our program is that our clusters span a range of
physical properties such as central concentration, cluster size, and mass--
essential ingredients in the formation, evolution, and dynamical roles of
cluster binaries. Exploiting this range of properties, we have identified a
relation that provides the first compelling link between the number of X-ray
sources and the predicted stellar encounter frequency in globular cluster
cores. But further progress in understanding the details implicit in this
relationship (e.g., whether CVs and qLMXBs formed primarily via stellar
encounters, while BY Dra's/RS CVn's are mainly primordial binaries) demands
uniform optical identifications for multiple clusters, spanning the full range
physical properties.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10121
Title:               The Core Dynamics of the Dense Globular Cluster NGC 6752
PI:                  Charles Bailyn
PI Institution:      Yale University

NGC 6752 is one of the best-studied dense globular clusters, and a wide
variety of intriguing and anomalous results have been obtained.  We propose
ACS imaging of the core of this cluster.  This will increase the accuracy of
our previous internal proper motion measurements by almost an order of
magnitude, providing an unprecedented probe of the central potential.  The
data will also greatly increase the radial extent of previous work on the
binary frequency and luminosity function of this cluster.  Together, the data
will provide a new level of constraints on the dynamics of a dense globular
cluster.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10122
Title:               Accretion in the closest binary systems known
PI:                  Danny Steeghs
PI Institution:      Smithsonian Institution Astrophysical Observatory

Recently, three variable stars have been identified as likely accreting binary
systems with ultra-short orbital periods. Optical and X-ray observations have
revealed periodicities of 5-10 minutes, making them the closest binaries known
as well as strong sources of gravitational wave emission. Such short-period
accreting binaries form the cornerstone to our understanding of binary
formation and evolution, in particular of the large double white dwarf
population in our galaxy, a candidate progenitor population for Type Ia
supernovae. We propose to obtain the first UV observations of these objects
using STIS in order to (i) determine the temperature of the primary and the
composition of their donor stars, (ii) correlate the UV variability with other
wavebands and determine if the periods are indeed orbital, (iii) look for
dynamical signatures of direct-impact accretion that is expected to govern the
survival rate of double white dwarfs. These UV observations are essential in
order to unequivocally determine whether these are indeed the most compact
binaries known.
================================================================================

Proposal Category:   GO
Scientific Category: AGN/QUASARS
ID:                  10123
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 measured by indirect techniques such as reverberation
mapping. An already approved CHANDRA Cycle 4 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: ISM AND CIRCUMSTELLAR MATTER
ID:                  10124
Title:               Physical Processes in Orion's Veil:  A High Resolution UV
                     Absorption Study of the Line of Sight towards the
                     Trapezium
PI:                  Gary Ferland
PI Institution:      University of Kentucky

Star formation is governed by a complex interplay among magnetic, thermal,
turbulent and gravitational energies.  Of these, magnetic energies are the
most difficult to measure.  Yet magnetic energies are crucial to the evolution
of molecular clouds if they are comparable to other energies.  Unfortunately,
magnetic field strength measurements are sparse.  Moreover, detailed field
strength maps exist in only one region of the ISM, the veil of neutral
material in front of the Orion Nebula.  From the Zeeman effect in 21cm HI
absorption lines, we have accurate maps of the line-of-sight field strength in
two independent velocity components of the veil.  Therefore, the veil presents
a unique laboratory for study of magnetic effects in star forming regions. We
have recently combined archival UV absorption line data with photoionization
models to estimate the veil's density, temperature and level of ionization.
On this basis, we infer that magnetic energies far exceed turbulent and
thermal energies in at least one HI velocity component.  This component is
magnetically unique.   All other data about star forming regions suggest
equipartition between magnetic and turbulent energies. Our analysis of
physical conditions in Orion?s veil suffers from an important limitation.
Existing UV absorption line data have insufficient spectral resolution to
separate the two HI velocity components.  Therefore, our models reflect
average conditions in the two components.  Yet actual conditions are likely to
be quite different since one component must lie closer to the source of
ionization. We propose to use STIS to obtain high resolution UV spectra of
Theta 1 Ori A.   These data will allow us to model the two velocity components
separately.  We can then estimate magnetic and other energies in the two
components.  We will determine if the apparent magnetic uniqueness of one
component applies to both, and we will estimate the distances of each
component from the ionizing stars.  This study will provide the most
comprehensive information obtainable about the role of magnetic effects in a
star forming region.
================================================================================

Proposal Category:   GO
Scientific Category: AGN/QUASARS
ID:                  10125
Title:               Where is the Wind in 1H0707-495?
PI:                  Karen Leighly
PI Institution:      University of Oklahoma Norman Campus

We propose three observations using HST STIS of the narrow-line  Seyfert 1
galaxy 1H 0707-495 to be coordinated with already-approved deep exposures
using FUSE.  A previous HST observation of 1H 0707-495 revealed strongly
blueshifted high-ionization lines, suggesting an origin in an outflowing wind.
Detailed photoionization modeling reveals that the wind line fluxes and ratios
are consistent with two solutions: a high-density, high-column solution,
originating close to the central engine, and a low-density, low-column
solution, located much further out.  These two locations, interestingly,
correspond to those predicted by two different physical models for winds in
AGNs. We can differentiate between these models by observing emission line
variability on two time scales, and examining relative variability of OVI
obtained by FUSE and CIV and other lines obtained by HST.  We will also look
for profile variability, constrain velocity ionization stratification through
a detailed study of the profiles, and investigate metallicity, which has been
suggested to be high in NLS1s. This program, requiring only a modest amount of
time, is expected to make significant contributions to our understanding of
outflows in AGN, and the structure, origin and metallicity of the broad-line
region.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10126
Title:               The 3-D Shape of the SMC: Is It Tidally Distorted?
PI:                  Edward Olszewski
PI Institution:      University of Arizona

We propose to exploit the exceptional spatial resolution of HST to
definitively show whether the SMC is tidally elongated along the line-of-
sight, and therefore the status of the Milky Way's interaction/destruction of
the Magellanic Clouds. We use BVI ACS images of several crowded SMC fields in
the region predicted by models of the orbit and tidal evolution of the
Magellanic Clouds (and by observations of Cepheids) to have a large depth. We
exploit the red clump feature (and the rarer true horizontal branch) to derive
the depth.  Specifically, we will observe six fields along the predicted
region of maximum distance gradient of the SMC, along with two ACS fields and
several WFPC2 fields in the archives, to map out the depth of the SMC in this
region. We are searching for substructure, such as a tidal tail, that may be
present.  Crowding in this region of the SMC is so severe that this project
cannot be done from the ground.
================================================================================

Proposal Category:   GO
Scientific Category: COSMOLOGY
ID:                  10127
Title:               IMAGING A PROTOCLUSTER AT z = 3.1: EFFECTS OF ENVIRONMENT
                     AND EVOLUTION ON GALAXY POPULATIONS IN THE EARLY UNIVERSE
PI:                  George Miley
PI Institution:      Universiteit Leiden

We propose imaging a rich protocluster, 0316-26 at z = 3.13, with 31 confirmed
Lya cluster members. The bright radio galaxy host is identified with the
progenitor of the dominant cluster galaxy. Because its redshift places Lya
into an ACS narrow-band filter, the protocluster provides a unique laboratory
for studying galaxies at a crucial epoch in the evolution of the Universe. We
shall (i) measure and compare sizes, morphologies and colors of galaxies from
populations detected using 4 different selection techniques (Lyman and 4000A
breaks, Lya and [OIII] excesses), (ii) study effects of an overdense
environment by comparing the properties of protocluster galaxies with z~3
field galaxies from GOODS, (iii) study effects of evolution by relating our
data to observations of similar protocluster/cluster targets at redshifts z =
4.1, 2.2, and 1.2, and (iv) constrain the formation of the most massive
cluster galaxies by investigating the spatial distribution, Lya equivalent
widths and other properties within the 5" radio galaxy host. The ultimate aim
is to disentangle the history of structure development and stellar evolution
for rich clusters of galaxies.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10128
Title:               Probing the Formation & Evolution of M31's Outer Disk and
                     Halo, Part II
PI:                  Annette Ferguson
PI Institution:      Max-Planck-Institut fur Astrophysik

Over the past several years, our group has conducted a large panoramic ground-
based imaging  survey of resolved luminous stars in M31 using the INT Wide-
Field Camera. Our now complete survey covers 40 square degrees around M31,
extending to a major axis distance of ~60 kpc. This survey has led to the
discovery of numerous spatial density and/or colour (metallicity?) variations
within the M31 halo and outer disk, and interim results motivated a successful
Cycle 11 HST/ACS program to obtain deep colour-magnitude diagrams for six
regions exhibiting the most prominent stellar substructure  known at that
time, including the giant stellar stream and the clump of stars near the
anomolous cluster, G1.  The present proposal requests time to augment our
Cycle 11 program with observations of two new features, a very low surface
brightness fragment lying 3 degrees north-east of center and a high surface
brightness spur of emission in the south-western half  of the galaxy, which we
have discovered since 2001.  Deep colour-magnitude diagrams  reaching 2-3
magnitudes below the horizontal branch will be constructed, allowing detailed
characterization of the luminous evolved stellar populations via the red giant
metallicity distribution, the luminous asymptotic giant branch, the horizontal
branch morphology and the red clump, as well as the detection of a main-
sequence that may be present from any younger component.  Together the Cycle
11 and 13 pointings target all prominent stellar substructure known to exist
within 60 kpc of M31.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10129
Title:               Resolving Globular Clusters in NGC 1399
PI:                  Thomas Puzia
PI Institution:      Space Telescope Science Institute

We intend to use the ACS/WFC to measure structural parameters (half light
radius, King core radius and concentration parameter) of individual globular
clusters (GCs) in NGC 1399. Very little is known about structural parameters
of globular clusters as a function of radius outside the Local Group. The
proposed observations, arranged in a 3x3 ACS mosaic, will allow us to perform
the first detailed wide-field study of structural parameters of globular
clusters in a giant elliptical galaxy. In particular we will: 1) study the
size-galactocentric distance relation of globular clusters out to ~55 kpc
(~1.6 eff. radius of the GCS) and determine whether the observed differences
in sizes between metal-rich and metal-poor globular cluster in early-type
galaxies are primordial and thereby reflect fundamental differences in
formation, or are due to projection effects; 2) match the GC position observed
with HST/ACS with X-ray binaries identified over the full Chandra field, and
use the above sizes to constrain physical models for X-ray binary formation in
GCs. 3) The wealth of ground-based data available for this system
(photometry+spectroscopy), will allow us to correlate the structural
properties with other GC properties, such as their chemical composition,
luminosity, etc.
================================================================================

Proposal Category:   SNAP
Scientific Category: STELLAR POPULATIONS
ID:                  10130
Title:               Systemic Proper Motions of the Magellanic Clouds from
                     Astrometry with ACS: II. Second Epoch Images
PI:                  Charles Alcock
PI Institution:      University of Pennsylvania

We request second epoch observations with ACS of Magellanic Cloud fields
centered on the 40 quasars in the LMC and SMC for which we have first epoch
Cycle 11 data. The new data will determine the systemic proper motion of the
Clouds. An extensive astrometric analysis of the first epoch data shows that
follow-up observations with a two year baseline will allow us to measure the
proper motion of the clouds to within 0.022 mas/year in each of the two
orthogonal directions (assuming that we can image 25 quasars, i.e., with a
realistic Snapshot Program completion rate). The best weighted combination of
all previous measurements has a seven times larger error than what we expect.
We will determine the proper motion of the clouds with 2% accuracy. When
combined with HI data for the Magellanic Stream this will constrain both the
mass distribution in the Galactic Halo and theoretical models for the origin
of the Magellanic Stream. Previous measurements are too crude for such
constraints. Our data will provide by far the most accurate proper motion
measurement for any Milky Way satellite. With the cancellation of SM4, HST is
expected to transition to two-gyroscope guiding in Cycle 14. This guiding mode
has additional jitter that will decrease the accuracy of all HST astrometry.
Moreover, there will be a 10 degree radius hole about the ecliptic poles that
will be unobservable, which regrettably includes the LMC. So this cycle may be
the last realistic opportunity for this fundamental measurement. If no second
epoch data are obtained, the previous investment of 40 snapshot orbits will be
wasted. There will be no other observatory for at least a decade that can make
this measurement.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10131
Title:               Determining the Origin of Virgo's Intracluster Stars
PI:                  Robin Ciardullo
PI Institution:      The Pennsylvania State University

Intracluster stars constitute about 20% of the total stellar population of a
typical galaxy cluster, and their existence provides a vital clue for our
understanding of cluster formation and evolution.   However, to exploit their
probative value, we need to know their origins:  are they the remnants of
dwarf galaxies, long since destroyed by the cluster potential, or have the
stars been harassed from their parent galaxies at recent epochs?  To answer
this question, we propose to use the Wide-Field Channel of ACS to make an I,
(V-I) color-magnitude diagram of Virgo's intracluster stars.  From the
position and morphology of the population's red giant branch, we will be able
to determine the metallicity distribution function of the stars, and thereby
determine their likely origin and ejection mechanisms.  Only HST with the ACS
has the sensitivity and resolution to perform this fundamental measurement.
This program has two options.  Option one uses conventional methods of cluster
photometry and requires 37 orbits of exposure time.  Option two involves a
novel analysis technique, which promises to achieve most of the same science
in two-thirds the time (23 orbits).  We describe this alternative method of
analysis and demonstrate its use via simulations.
================================================================================

Proposal Category:   SNAP
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID:                  10132
Title:               UV Confirmation of New Quasar Sightlines Suitable for the
                     Study of Intergalactic Helium
PI:                  Scott Anderson
PI Institution:      University of Washington

The reionization of intergalactic helium is thought to have occurred between
redshifts of about 3 and 4. The study of HeII Lyman-alpha absorption towards a
half-dozen quasars at 2.72.9 SDSS quasars, but with special emphasis
on extending helium studies to the highest redshift sightlines. Our proposed
approach has already proven successful, and additional sightlines will enable
follow-up observations at higher S/N with STIS to measure the spectrum and
evolution of the ionizing background radiation, the density of intergalactic
baryons, and the epoch of reionization of the IGM.
================================================================================

Proposal Category:   GO
Scientific Category: AGN/QUASARS
ID:                  10133
Title:               HST / Chandra Monitoring of a Dramatic Flare in the M87
                     Jet
PI:                  John Biretta
PI Institution:      Space Telescope Science Institute

As the nearest galaxy with an optical jet, M87 affords an unparalleled
opportunity to study extragalactic jet phenomena at the highest resolution.
During 2002, HST and Chandra monitoring of the M87 jet detected a dramatic
flare in knot HST-1 located ~1" from the nucleus.  As of late 2003 its
brightness has increased twenty-fold in the optical band, and continues to
increase sharply; the X-rays show a similarly dramatic outburst. In both bands
HST-1 now greatly exceeds the nucleus in brightness. To our knowledge this is
the first incidence of an optical or X-ray outburst from a jet region which is
spatially distinct from the core source; this presents an unprecedented
opportunity to study the processes responsible for non-thermal variability and
the X-ray emission.  We propose seven epochs of HST/STIS monitoring during
Cycle 13, as well as seven epochs of Chandra/ACIS observation (5ksec each). We
also include a brief HRC/ACS observations that will be used to gather spectral
information and map the magnetic field structure.  This monitoring is
continued into Cycles 14 and 15.  The results of this investigation are of key
importance not only for understanding the nature of the X-ray emission of the
M87 jet, but also for understanding flares in blazar jets, which are highly
variable, but where we have never before been able to resolve the flaring
region in the optical or X-rays.  These observations will allow us to test
synchrotron emission models for the X-ray outburst, constrain particle
acceleration and loss timescales, and study the jet dynamics associated with
this flaring component.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10134
Title:               The Evolution and Assembly of Galactic Disks: Integrated
                     studies of mass, stars and gas in the Extended Groth
                     Strip
PI:                  Marc Davis
PI Institution:      University of California - Berkeley

We propose a 126 orbit total F606W/F814W ACS imaging program to measure the
evolution of galaxy disks from redshift z=1.4 to the present.  By combining
HST imaging with existing observations in the Extended Groth Strip, we can for
the first time simultaneously determine the mass in dark matter that underlies
disks, the mass in stars within those disks, and the rate of formation of new
stars from gas in the disks, for samples of >1,000 objects.  ACS observations
are critical for this work, both for reliable identifications of disks and for
determining their sizes and inclinations.  Combining these with the kinematics
measured from high-resolution Keck DEIMOS spectra will give dynamical masses,
which include dark matter.  Stellar masses can be measured separately from
dark matter using ground-based BRIK and Spitzer IRAC GTO data, while cross-
calibrated star formation rates will come from DEEP2 spectra, GALEX, and
Spitzer/MIPS.  The field chosen is the only one where all multiwavelength
needed will be available in the near term.  This data will show how the
fundamental properties of disks (luminosity, rotation speed, scale length) and
their scaling relations have evolved since z~1, and also will measure the
buildup of stellar disks directly; these avenues will provide fundamental
tests of models of disk formation and evolution.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10135
Title:               Unveiling the Progenitors and Physics of Cosmic
                     Explosions
PI:                  Shrinivas Kulkarni
PI Institution:      California Institute of Technology

GRBs and XRFs are clearly highly asymmetric explosions and require a long-
lived power source (central engine). In contrast, nearby core-collapse events
are essentially spherical explosions.  However, the failure of spherical
neutrino driven collapses has led to the idea that asymmetric energy release
is essential for the explosion. The recent finding of a Type Ic SN in GRB
030329, the association of the low energy event GRB 980425 with SN 1998bw, the
theoretical development discussed above and the rise of collapsar models make
it timely to consider whether all these explosions contain engines.  Given the
uncertainties in theoretical modeling it is clear that observations are needed
to guide models. A priori there is little reason to expect connection between
the ultra-relativistic jet that powers the GRB and the explosive
nucleosynthesis of the ~0.5 solar masses of Nickel-56 that powers the
accompanying supernova.  We propose a comprehensive program of ACS photometric
searches (and measurements) for SNe associated with GRBs and XRFs.  In
concert, we will undertake ground-based spectroscopy to determine velocity
widths, and measure engine parameters from pan-chromatic afterglow
observations.  Our goal is to produce a comprehensive database of engine and
SN physical parameters against which theoretical modeling will be guided.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10136
Title:               Post-AGB Stars in the Halo of M81
PI:                  Howard Bond
PI Institution:      Space Telescope Science Institute

Post-asymptotic-giant-branch (PAGB) stars of spectral types A-F are the
brightest members of Population II.  We have shown, using ground-based
observations, that PAGB stars have tremendous potential as highly efficient
standard candles and as tracers of halo populations and late stellar
evolution.  Our analysis of PAGB stars in archival HST images of M32, based on
the equivalent of one orbit of HST time, precisely reproduces the accepted
distance.    We propose to obtain ACS/WFC and WFPC2 images of fields in the
halo of M81, as another test of the PAGB method.  We show that 4 orbits of HST
data will produce a distance of comparable accuracy to the much more laborious
Cepheid technique.  If successful on M81, we will propose in the next cycle to
measure the distance to Virgo using our method, a distance ladder that has
only two rungs (trigonometric parallaxes of subdwarfs to calibrate PAGB stars
in globular clusters, and then PAGB stars in Virgo).
================================================================================

Proposal Category:   SNAP
Scientific Category: GALAXIES
ID:                  10137
Title:               Cluster Archeology: The Origin of Ultra-compact Dwarf
                     Galaxies
PI:                  Michael Drinkwater
PI Institution:      University of Queensland

Ultra-compact dwarf (UCD) galaxies are a new type of galaxy we have discovered
in the central regions of the Fornax and Virgo galaxy clusters. Our most
recent observations in the Fornax Cluster show that UCDs outnumber normal
galaxies in the centre of that cluster. Here we propose snapshot imaging of
UCDs in the Fornax and Virgo clusters to test theories of how these
fascinating objects formed.  In particular we wish to image Virgo cluster UCDs
for which we have ground-based Keck spectroscopy to test predictions that they
formed more recently than the Fornax UCDs.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10138
Title:               Searching for the Bottom of the Initial Mass Function
PI:                  Kevin Luhman
PI Institution:      Smithsonian Institution Astrophysical Observatory

The minimum mass of the Initial Mass Function (IMF) should be a direct
reflection of the physical processes that dominate in the formation of stars
and brown dwarfs. To date, the IMF has been measured down to 10 M_Jup in a few
young clusters; there is no sign of a low-mass cutoff in the data for these
clusters. We propose to obtain deep images in the SDSS i and z filters (i=26,
z=25) with the ACS/WFC on HST for a 800"x1000" field in the Chamaeleon I star-
forming region (2 Myr, 160 pc). By combining these HST data (0.8, 0.9 um) with
comparably deep broad-band photometry from ground-based telescopes (1.2, 1.6,
2.2 um) and SIRTF (3.6, 4.5, 5.8, 8.0 um), we will measure the mass function
of brown dwarfs down to the mass of Jupiter and thus determine the lowest mass
at which objects can form in isolation in a typical star forming cluster.
================================================================================

Proposal Category:   GO
Scientific Category: AGN/QUASARS
ID:                  10139
Title:               Structure of the Accretion Disk in the NLS1 NGC 4051
PI:                  Bradley Peterson
PI Institution:      Ohio State University

We propose to obtain a UV spectrum of the narrow-line Seyfert 1 (NLS1) galaxy
NGC 4051 on a target-of-opportunity basis when it goes into a faint state for
the purpose of exploring the variable nature of the shape of the ionizing
continuum in this source. Previous simultaneous X-ray and optical monitoring
of this source reveals that at some times the X-rays and the He II 4686
emission line nearly disappear, while the UV/optical continuum and Balmer
lines are weaker, but present and continue to vary. This suggests that there
is a variable cutoff in the shape of the ionizing continuum, and in the faint
state this occurs at low enough energies to affect all the strong UV lines. By
comparing emission-line flux ratios in the low state to those in high states
and with photoionization equibrium calculations, we can identify the cutoff
energy. The cutoff energy may correspond to a transition radius in the
accretion disk, inside of which the source has entered into a low-radiative
efficiency mode.
================================================================================

Proposal Category:   GO
Scientific Category: SOLAR SYSTEM
ID:                  10140
Title:               Identification of a magnetic anomaly at Jupiter from
                     satellite footprints
PI:                  Denis Grodent
PI Institution:      Universite de Liege

Repeated imaging of Jupiter's aurora has shown that the northern main oval has
a distorted 'kidney bean' shape in the general range of 90-140ј System III
longitude, which appears unchanged since 1994. While it is more difficult to
observe the conjugate regions in the southern aurora, no corresponding
distortion appears in the south. Recent improved accuracy in locating the
satellite footprint auroral emissions has provided new information about the
geometry of Jupiter's magnetic field in this and other areas. The study of the
magnetic field provides us with insight into the state of matter and the
dynamics deep down Jupiter. There is currently no other way to do this from
orbit. The persistent pattern of the main oval implies a disturbance of the
local magnetic field, and the increased latitudinal separation of the locus of
satellite footprints from each other and from the main oval implies a locally
weaker field strength. It is possible that these phenomena result from a
magnetic anomaly in Jupiter's intrinsic magnetic field, as was proposed by A.
Dessler in the 1970's. There is presently only limited evidence from the
scarcity of auroral footprints observed in this longitude range. We propose to
obtain HST UV images with specific observing geometries of Jupiter to
determine the locations of the auroral footprints of Io, Europa, and Ganymede
in cycle 13 to accurately determine the magnetic field geometry in the
suggested anomaly region, and to either confirm or refute the suggestion of a
local magnetic anomaly.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10141
Title:               UV spectroscopy of the hot bare stellar core H1504+65
PI:                  Klaus Werner
PI Institution:      Universitat Tubingen, Institut fur Astronomie &
                     Astrophysik

H1504+65 ist the hottest known white dwarf (Teff=200 000 K). It has an
extraordinary surface composition. The photosphere is devoid of hydrogen and
helium. It is mainly composed of carbon and oxygen (by equal parts) and neon
(2%). We obviously see the exposed core of a former red giant. The
evolutionary history of this unique object is unknown. We have identified
magnesium absorption lines in the soft X-ray photospheric (Chandra) spectrum,
which suggests that H1504+65 may be a O-Ne-Mg white dwarf. We will test this
hypothesis by abundance determinations of Mg and Na. If confirmed, then
H1504+65 would be the most compelling case for the existence of single O-Ne-Mg
white dwarfs.
================================================================================

Proposal Category:   GO
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID:                  10142
Title:               The connection between star-forming galaxies and low-
                     redshift quasar absorption line systems
PI:                  Regina Schulte-Ladbeck
PI Institution:      University of Pittsburgh

We have positionally matched our database of over 19,000 star-forming galaxies
(SFGs) from the Sloan Digital Sky Survey (SDSS) against the SDSS QSO catalog.
This has allowed us to discover nineteen bright QSOs with redshifts of less
than or about one behind local SFGs. Two of the QSOs were fortuitously already
observed with HST, and show strong Lyman alpha lines at the emission-line
redshifts of the SFGs with which we matched them
================================================================================

Proposal Category:   SNAP
Scientific Category: COOL STARS
ID:                  10143
Title:               Ultracool companions to the nearest L dwarfs
PI:                  I. Reid
PI Institution:      Space Telescope Science Institute

We propose to conduct the most sensitive survey to date for low mass
companions to nearby L dwarfs. We will use NICMOS to image targets drawn from
a volume-complete sample of 70 L dwarfs within 20 parsecs. The combination of
infrared imaging and proximity will allow us to search for T dwarf companions
at separations as small as 1.6 AU. This is crucial, since no ultracool
binaries are currently known with separations exceeding 15 AU. Only 10 dwarfs
in this sample have previous HST observations, primarily at optical
wavelengths.  With the increased sensitivity of our survey, we will provide
the most stringent test to date of brown dwarf models which envisage their
formation as ejected stellar embryos. In addition, our observations will be
capable of detecting binaries with mass ratios as low as 0.3, and will
therefore also test the apparent preference for equal-mass ultracool binaries.
Finally, our observations offer the best prospect to date of detecting
companions significantly cooler than the coolest T dwarf currently known.
================================================================================

Proposal Category:   GO
Scientific Category: SOLAR SYSTEM
ID:                  10144
Title:               The Gas Environment of Comet 9P/Tempel 1 During the Deep
                     Impact Encounter
PI:                  Paul Feldman
PI Institution:      The Johns Hopkins University

We propose a series of observations of the periodic comet 9P/Tempel 1 in
conjunction with NASA's Deep Impact mission.  This mission is a spacecraft
that will release a 360 kg impactor into the nucleus of the comet on July 4,
2005.  Our primary objective is to study the generation and evolution of the
gaseous coma resulting from this impact.  To this end we plan to obtain
ultraviolet spectra with STIS before, during, and following the impact.  As a
secondary objective we will obtain wide-band images of the visual outburst
resulting from the impact.  We also plan to use the high resolution capability
of the ACS/HRC, in conjunction with the camera on board the spacecraft, two
weeks prior to impact, to determine the spatial orientation of active jets
emanating from the comet's nucleus and to assess the potential hazards of
these jets to the spacecraft.
================================================================================

Proposal Category:   GO
Scientific Category: STAR FORMATION
ID:                  10145
Title:               Physical parameters of the upper atmosphere of the
                     extrasolar planet HD209458b
PI:                  Alfred Vidal-Madjar
PI Institution:      CNRS, Institute d'Astrophysique de Paris

Every 3.5 days, the transits of the gaseous planet orbiting HD209458 offers
the unique opportunity to investigate the spectral features of an extra-solar
planetary atmosphere. Using HST, we first discovered the extended upper
atmosphere of HD209458b through the detection of a 15% HI absorption. We
concluded that the hydrogen must be escaping the planet with a lower limit of
10^10 g/s (Vidal-Madjar et al. 2003, Nature 422, 143). With additional
observations, we subsequently detected OI and CII in the upper atmosphere
showing that this atmosphere is hydrodynamically escaping (in "blow off",
Vidal-Madjar et al. 2004).  Here we propose to further study this upper
atmosphere to better constrain the "blow off" state by directly estimating the
physical conditions and the flow characteristics. In particular we will
determine the temperature and density distribution in the upper atmosphere,
the density at the Roche lobe, the limit between the lower and upper
atmosphere and their ionization states. Comparison between the optical and
near ultraviolet occultation light curves will provide useful information on
the molecular/haze content of the lower atmosphere.  The observation of six
HD209458b transits with a single E230M setting will allow the detection of
many lines adressing these issues. The proposed observations will give us for
the first time a detailed probe of the atmosphere of an "evaporating" extra-
solar planet.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10146
Title:               Solving the problem of the White Dwarf Cooling Sequence
                     End in M4: an efficent approach
PI:                  Luigi Bedin
PI Institution:      Universita di Padova

The end of the white dwarf (WD) cooling sequence (WDCS) has never been
observed, despite the importance that it has in providing an age estimate of
old stellar systems, independent from the standard method of the main sequence
turn off.  The best targets for this investigation are the closest stellar
clusters, and, among them, globular clusters are the most interesting ones.
Being the oldest stellar aggregates, they allow to probe the advanced WD
cooling phases, and the independent age estimate coming from the end of their
WDCS has an important cosmological impact.  M4 is the best target for this
investigation. Despite huge observational efforts, we still miss the end of
its WDCS. The ACS camera offers a unique opportunity to identify it. Coupled
with already existing observations, we here prove that we can finally reach it
with only 10 HST orbits. This is probably the last opportunity we have for a
large number of years. The data we are requesting here, will also be used to
complete other two programs of great astrophysical impact: the observational
detection of the main sequence hydrogen burning limit, and the measurement of
the geometrical distance of M4.
================================================================================

Proposal Category:   GO
Scientific Category: COOL STARS
ID:                  10147
Title:               Detecting the elusive low mass companion around epsilon
                     Indi
PI:                  Michael Endl
PI Institution:      University of Texas at Austin

We propose coronagraphic NICMOS observations of the nearby (d = 3.6 pc) K5V
star epsilon Indi (HD 209100) to search for the unknown companion which causes
a low amplitude radial velocity (RV) trend in our 11 years of precise Doppler
measurements. This RV data set places a lower limit of 4.5 AU for the orbital
semimajor axis of this companion.  Moreover, the fact that the RV trend is
lacking any sign of curvature over this long time period clearly points
towards a much larger orbital separation. Epsilon Indi also has a T dwarf
(binary) companion at a separation of 1400 AU.  However, these brown dwarf
companions are too distant from the primary to induce the observed RV
variation. It is also unlikely that this nearby star has an unknown stellar (M
dwarf) companion.  The RV signal is thus most probably caused by a yet unknown
giant planetary or brown dwarf companion at a separation of more than 5 AU.
Because epsilon Indi is so near to the Sun, it constitutes an ideal target for
high contrast imaging with NICMOS in its coronagraphic mode.  Indeed, NICMOS
coronagraphy is capable of detecting objects down to 15 Jupiter masses at
separations greater than 2.3 arcseconds (S/N=25) - precisely the separation
and mass range indicated by our Doppler spectroscopy.  Only 2 orbits of
HST/NICMOS observations could directly image the coolest and lowest mass
companion ever found around a solar-type star.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10148
Title:               The Masses of the Ultraluminous X-Ray Sources
PI:                  Joel Bregman
PI Institution:      University of Michigan

Ultraluminous X-ray sources are non-nuclear sources in normal disk galaxies
that are second only to AGNs in point-source luminosity.  These enigmatic
objects are either stellar mass black holes that are super-Eddington emitters,
or sub-Eddington emission from 1E3-1E4 Msolar black holes. We can distinguish
between these models by a direct determination of the mass of the primary,
which requires knowing the spectral type of the secondary, its period, and its
orbital velocity around the black hole.  We propose to obtain UV spectra to
determine the spectral type of two ULX secondaries (optical counterparts), to
infer the masses and radii of the secondaries and their suitability for radial
velocity studies.  For another ULX secondary, we already obtained a UV
spectrum showing it to be a B0I star, so we propose three additional
observations, which will yield the characteristic orbital velocity, help
constrain the period, and reveal if the primary is a 1E3-1E4 Msolar black
hole, which would produce velocities > 1000 km/sec.
================================================================================

Proposal Category:   GO
Scientific Category: AGN/QUASARS
ID:                  10149
Title:               The Coevolution of Supermassive Black Holes and Galaxies
                     at z~3
PI:                  Chien Peng
PI Institution:      University of Arizona

The existence of strong correlations between the mass of supermassive black
holes and galaxy bulge properties implies that there is an intimate connection
between their formation and evolution.  How do supermassive black holes grow
and how did the correlations come about?  Is the growth of supermassive black
holes coeval with the growth of the bulge, and is a bulge necessary for AGN
activity at high z?   We propose to use HST NICMOS to image 9 low-luminosity
broad-line AGNs at z~3 in the restframe B-band, identified through the Lyman-
break technique.  This sample is unique because the AGN luminosities are
comparable to Seyfert-like nuclei at z~3, and thus are some of the lowest that
have been selected optically.  Because of the low total luminosity of the
sample, the hosts are likely to be Lyman-break galaxies, which are believed to
be the progenitor galaxies of the local Hubble sequence. The goal is to
directly detect their host galaxies and to separate the AGN, in order to study
the host galaxy morphology and luminosity.  From measurement of the bulge
luminosity and black hole mass (through available spectra), we will study the
black hole-bulge coevolution out to z~3.  We will also compare the luminosity
and morphology of these faint AGN hosts with the more luminous and massive
host galaxies found in previous HST studies of quasars.
================================================================================

Proposal Category:   GO
Scientific Category: COSMOLOGY
ID:                  10150
Title:               NICMOS observations of A1689
PI:                  Narciso Benitez
PI Institution:      Instituto de Astrofisica de Andalucia (IAA)

The potential of galaxy clusters as ``cosmic telescopes'' has been known for a
long time, but practical results in the pre-ACS era have been scarce due to
two main problems: the uncertainty in determining the magnification
distribution of the cluster (the ``optics''  of the instrument) and the
presence of numerous bright cluster galaxies which cover the field of view and
hinder the detection of background galaxies. We have developed techniques to
solve these two problems working with our ACS observations of A1689, the most
powerful lens in the sky, and for the first time we have been able to
determine the "specifications" of a cosmic telescope with a useful level of
precision, thanks to the detection and identification of more than 100
multiple images with reliable redshift information. We propose to observe the
high magnification region in the A1689 field in the F110W band with a 3x3
mosaic of NIC3 pointings; the resulting image will reach a limiting magnitudes
of 29.5, surpassing in depth the UDF NICMOS observations and providing an
unique dataset with multiple scientific returns.
================================================================================

Proposal Category:   GO
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID:                  10151
Title:               Testing the Warm-Hot Intergalactic Medium Paradigm
PI:                  J. Howk
PI Institution:      University of California - San Diego

Cosmological hydrodynamical simulations predict that ~30%-40% of the low-
redshift baryons reside in a collisionally ionized phase (log T ~ 5 to 7) of
the intergalactic medium (IGM) associated with large-scale, unvirialized
filaments of galaxies.  Recent surveys of O VI gas have lent some support to
the presence of this warm-hot intergalactic medium (WHIM), but the results are
significantly limited by uncertainties in the ionization mechanism (photo- vs.
collisionally ionized) and metallicity of the gas.  We are pursuing a large
program to test predictions of the WHIM and to improve existing measurements
of the OVI absorbers.  The primary goals are (i) to increase the redshift path
for detection of the hottest IGM, previously only accessible through X-ray
absorption studies, using EUV absorption from Ne VIII and Mg X, and (ii) to
constrain the IGM physics using UV absorption from H I Ly-alpha, C III, C IV,
and O VI.  Our team has been awarded a FUSE Legacy program to probe the
moderate-redshift WHIM using unique ionization diagnostics in the restframe
EUV waveband, including O V, Ne VIII and Mg X.  Here we propose to complement
our FUSE Legacy program with STIS intermediate-resolution echelle-mode
observations of five moderate-redshift (0.45 < z < 0.98) AGNs.  The unique
combination of FUSE EUV and STIS UV spectra will allow us (1) to test the
current models of the WHIM by studying the ionization mechanisms responsible
for producing highly-ionized metals in the IGM and determining the frequency
of genuine high-temperature metal absorbers in the low-redshift IGM; (2) to
investigate the relationship between WHIM and large-scale galaxy structures
using galaxy redshift measurements obtained with DEIMOS on Keck and IMACS at
Las Campanas Observatory; and (3) to determine the ionization state and
metallicity of O VI absorbers in order to accurately assess their contribution
to the total baryon budget.  Finally, we will make high-level science products
derived from these data freely available to the general astronomical
community.
================================================================================

Proposal Category:   SNAP
Scientific Category: COSMOLOGY
ID:                  10152
Title:               A Snapshot Survey of a Complete Sample of X-ray Luminous
                     Galaxy  Clusters from Redshift 0.3 to 0.7
PI:                  Megan Donahue
PI Institution:      Michigan State University

We propose a public, uniform imaging survey of a well-studied, complete, and
homogeneous sample of X-ray clusters. The sample of 73 clusters spans the
redshift range between 0.3-0.7. The samples spans almost 2 orders of magnitude
of X-ray luminosity, where half of the sample has X-ray luminosities greater
than 10^44 erg/s (0.5-2.0 keV). These snapshots will be used to obtain a fair
census of the  the morphology of cluster galaxies in the cores of clusters, to
detect radial and tangential arc candidates, to detect optical jet candidates,
and to provide an approximate estimate of the shear signal of the clusters
themselves, and potentially an assessment of the contribution of large scale
structure to lensing shear.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10153
Title:               Multi-wavelength Observations of Symbiotic Stars in
                     Outburst
PI:                  Charles Keyes
PI Institution:      Space Telescope Science Institute

To investigate the cause and nature of classical symbiotic outbursts, we
initiated a program of multi-wavelength observations of these events.  As
evidence is mounting that collimated outflows (jets) may be associated with
symbiotic outbursts, we also investigate conditions needed for jet production
- a question with broad astrophysical relevance.  The first target for our
campaign - the 2000-2002 outburst of Z Andromedae - confirmed the utility and
need for coordinated multi-wavelength observations to make progress in
understanding the nature of the outburst mechanisms in symbiotic stars.  FUSE
data were the cornerstone of that project (which included data from the VLA,
MERLIN, ground-based spectroscopy and photometry, Chandra, and XMM, but not
HST).  Our Z And observations have motivated us to propose a new scenario that
we term the "combination nova" which is triggered by a disk-instability.  To
test this new model, we received HST Cycle 12 and FUSE Cycle 4 time (through
approximately 6/2004) to continue the multi-wavelength approach with
observations at several epochs during the outburst of a second target-of-
opportunity (TOO).  That TOO has not yet been triggered. We propose here to
continue this TOO observing opportunity into Cycle 13 (to 7/2005).  FUSE Cycle
5 observations (to mid-2005) were recently approved.  Coordinated XMM and VLA
observations are also approved.  The evolution of the UV spectrum throughout
the outburst plays a vital role in distinguishing between the outburst models
currently in contention for describing outburst behavior.  Analysis of our
first campaign has shown that HST observations can play a fundamental role in
the multi-wavelength approach.  The combination of high-resolution STIS and
FUSE-band emission and absorption features, time-tagged observations, and
continua provide a unique opportunity to probe the structure and ionization
conditions in the outburst material that can not be accomplished with either
ultraviolet region alone.
================================================================================

Proposal Category:   GO
Scientific Category: COSMOLOGY
ID:                  10154
Title:               Morphology of z ~ 7-10 galaxies viewed through
                     gravitational telescopes
PI:                  Roser Pello
PI Institution:      Observatoire Midi-Pyrenees

The aim of these observations is to obtain deep z/ACS and H/NICMOS images in
the core of two lensing clusters, A1835 and AC114, where a few z ~ 7-10 galaxy
candidates have been selected from our ultra-deep JHK imaging program with
Isaac/VLT. Spectroscopic observations have allowed to confirm 2 of these
candidates thanks to the detection of faint emission lines identified as Lyman
alpha at z=7.2 and 10. Our HST project is focused on two main goals:  (1) the
morphological confirmation  of galaxy candidates lying near critical lines,
and  (2) the determination of the physical scales involved in star-forming
regions at z ~ 7-10.  These goals should have important implications on our
present knowledge of the galaxy formation process in the early Universe.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10155
Title:               A Mini-Survey of Interstellar Abundances in the
                     Magellanic Clouds
PI:                  Daniel Welty
PI Institution:      University of Chicago

Studies of the interstellar medium in the Magellanic Clouds explore somewhat
different environmental conditions from those typically probed in our own
Galactic ISM.  Apart from a few studies of individual sightlines, however,
little is known about the abundances and depletions in the ISM of the LMC and
SMC.   HST spectra of three SMC stars indicate that Si and Mg (generally
thought to be major dust constituents) are essentially undepleted in the SMC
gas --- even for components with severe depletions of Fe and Ni.  Similar
"anomalous" Si depletions have now been seen in cycle 12 STIS spectra of one
LMC star, though "normal" Si  depletions are seen toward a second.
Intriguingly, the "anomalous" Si depletions are all found for sightlines which
probe regions where the 2175 A extinction bump is either absent (most of SMC)
or very weak (LMC2). We therefore propose a mini-survey of interstellar
absorption lines toward 13 stars distributed throughout the LMC and SMC ---
which would more than double the number of Magellanic Clouds sightlines with
extensive  and accurate interstellar abundance information.  A single STIS
E230M setting will include lines from Zn II,  Si II, Fe II, Ti II, Cr II, Ni
II, and several trace neutral species --- allowing the abundance/depletion
pattern to  be determined at many locations in the two galaxies.  The analysis
of these spectra will have significant  implications for (1) making models of
interstellar dust grains (which currently rely heavily on silicates);  (2)
understanding the relationships between depletions, dust, and H_2 (which may
be somewhat different  in the Milky Way, LMC, and SMC); and (3) interpreting
the gas-phase abundances observed for more distant  low-metallicity systems,
such as the QSO absorption-line systems (which exhibit some similar
properties).
================================================================================

Proposal Category:   GO
Scientific Category: SOLAR SYSTEM
ID:                  10156
Title:               Saturn's Auroral Energy Deposition Coordinated with
                     Cassini UVIS
PI:                  John Clarke
PI Institution:      Boston University

An in-depth study of Saturn's magnetosphere and auroral processes has begun in
Jan. 2004 with coordinated HST STIS images of Saturn's aurora while the
approaching Cassini measures the solar wind.  This program is expected to
establish the degree of solar wind control of Saturn's aurora.  The beginning
of the Cassini orbiter tour of the Saturn system in July 2004 will offer new
opportunities for collaborative science.  The energetics of Saturn's auroral
processes can best be studied via low resolution UV spectra of the emissions
and the auroral "color ratio".  The geometry of the initial Cassini orbits
provides the best observing geometry for UVIS measurements of auroral
energetics when it is close to Saturn on the night side.  At such times, it
will be possible to have simultaneous observations of Saturn's southern /
dayside aurora with HST STIS and the northern / nightside aurora with Cassini
UVIS.  Both the distributions of the auroral emissions and the energy of the
precipitating particles can be measured simultaneously at conjugate points
north and south.  This proposal is to conduct one such simultaneous
observation, which will demonstrate the potential for future cycles.  We
request 5 HST orbits to observe a large fraction of one complete Saturn
rotation at the same time as Cassini UVIS.  The rotational coverage has been
shown to be of central importance in recent STIS images of Saturn's auroral
activity, which is concentrated in an "active sector" connected with the
strongest SKR radio emissions.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10157
Title:               Bulges or disks in the centers of late-type spirals?
PI:                  C. Carollo
PI Institution:      Eidgenossiche Technische Hochschule (ETH)

In a simple view of the Hubble sequence, smaller bulges should be rescaled
versions of bigger bulges. Bulges however have been found to change their
structural properties with decreasing luminosity, approaching at the faintest
end a disk-like, exponential light profile. This indicates a complex mass-
dependent bulge formation history. Particularly, the intermediate-to-small
size bulges have been suggested to form due to secular evolution processes
within their host disks. However, the alleged small bulges may even be
'simply' denser inner regions of the disks. Two major ingredients are missing
in order to (a) understand the nature of  bulges in the disk-dominated
galaxies, (b) establish whether and which secular evolution processes actually
occur, and (c) in which mass range they are preferentially active:  (1) High-
resolution numerical simulations of disk secular evolution, to provide a
quantitative basis for interpreting real data; (2) Observational diagnostics
which can break the degeneracy between very cold, dense disks and relatively
hot bulges, and to compare with the simulations. We are carrying out a large
N-body + SPH simulations campaign to settle the first issue.   Stellar
kinematics are the ideal observational diagnostics. We have acquired ground
kinematic data for the medium-sized bulges. However, both the spectroscopic
and  the spatial resolution requirements  necessary to trace the relative
contributions of cold and hot motions become  very stringent at the faint-end
of the bulge sequence: only the HST can provide radially-extended kinematics
for the smallest bulges.  We therefore ask for STIS/G750M spectroscopy to
measure internal resolved stellar kinematics for two small bulges selected
from our previous HST imaging program. Even just these two "data-points"  in
this unexplored mass-regime will allow significant progress in the
understanding of the origin of the Hubble sequence: Complemented by our
ground-study of the medium-sized bulges, they will allow us to establish
whether the ratio of cold-to-hot motions  in bulges in the intermediate-to-
small mass regime depends on the bulge mass, and, by comparing with our
simulations, to constrain the initial conditions and physical parameters that
allow disk secular evolution processes  to grow central bulges similar to
those that are observed along the entire Hubble sequence.
================================================================================

Proposal Category:   GO
Scientific Category: COSMOLOGY
ID:                  10158
Title:               ACS Observations of the Gravitational Lens B1608+656:
                     Characterizing the Einstein Ring
PI:                  Christopher Fassnacht
PI Institution:      University of California - Davis

We request time to obtain ACS deep images of the B1608+656 gravitational lens
system to fully characterize its enclosing Einstein ring with high signal-to-
noise ratio (SNR).  These data will allow us to determine the gravitational
potential of the lens, locally, to several percent accuracy and, combined with
the three independent time delays, measure H_0 to much better than 10%
precision.  For this goal, we have developed powerful new lens modeling codes
that make use of the full brightness distribution of the Einstein ring in lens
systems.  The B1608+656 system is ideal for our new code.  It has precisely
measured time delays, a well-determined stellar velocity dispersion, and an
Einstein ring that is not dominated by the lensed nuclear emission of the
background source.  When combined with high-SNR images of Einstein rings, the
new modeling codes provide qualitatively different and much improved analysis
of the ring emission than was previously possible.  The proposed ACS
observations will reach the SNR at which the new modeling code can be fully
exploited (SNR=5 per pixel).  Our simulations show that these new data will
allow us to reduce the total uncertainties in H_0 derived from the system by
at least a factor of two, to the 5-7% level for this system.
================================================================================

Proposal Category:   GO
Scientific Category: COSMOLOGY
ID:                  10159
Title:               Characterizing the Sources Responsible for Cosmic
                     Reionization
PI:                  Richard Ellis
PI Institution:      California Institute of Technology

Our group has demonstrated the role that massive clusters of galaxies, acting
as powerful cosmic lenses, can play in locating sources with modest mass and
star formation rate beyond redshifts z~5-6 likely to be representative of
those responsible for cosmic reionization.  The large magnifications, possible
in the critical regions of well-constrained clusters, bring sources into view
that would lie at or beyond the limits of conventional exposures such as the
UDF. Recently, using deep ACS and NICMOS imaging, we have located a low mass
source at z=7.05 whose UV continuum slope is apparently steeper than for
normal star-forming galaxies. We propose a deep ACS grism exposure to confirm
the nature of this source and further ACS and NICMOS imaging of well-studied
clusters to locate further examples.  The grism spectroscopy will conclusively
determine the UV SED of this source and our 3-color survey will constrain the
redshift, star-formation rate, and SED of additional 66.5, with more than 2.5 Msun/yr of star formation (our survey
limit).  Before the advent of the next generation of observational facilities,
our search technique may represent the only way to reliably select and
characterize the likely  population of galaxies during the epoch of
reionization.
================================================================================

Proposal Category:   GO
Scientific Category: AGN/QUASARS
ID:                  10160
Title:               The nuclear scattering geometry of Seyfert galaxies
PI:                  Andrew Robinson
PI Institution:      Rochester Institute of Technology

Orientation-based unification schemes are now well-established as the basis
for understanding the relationships between different classes of AGN. However,
our recent study of the optical polarization properties of Seyfert 1 galaxies
indicates that scattered light emerging from these objects often follows a
different path to that in Seyfert 2's, indicating that the simplest
unification geometry is incomplete. We have developed a generic scattering
model for Seyfert nuclei which includes a compact, equatorial scattering
region located within the circum-nuclear torus and the 'classic' polar
scattering region outside it. We propose to test this model by using NICMOS to
make NIR imaging observations that will allow us to isolate the two scattering
regions within individual objects.
================================================================================

Proposal Category:   GO
Scientific Category: SOLAR SYSTEM
ID:                  10161
Title:               Fresh ammonia-ice on Jupiter: The northern equatorial
                     region.
PI:                  Michael Wong
PI Institution:      University of California - Berkeley

The proposed multi-band imaging of one of the most dynamic regions on Jupiter
will complement recent space-based infrared datasets and will provide crucial
constraints to models of Jovian atmospheric dynamics. NICMOS is sensitive to
the jovian troposphere at and above the visible cloud decks. We selected six
NICMOS filters with varying levels of atmospheric opacity to observe cloud
features as they rotate from the central meridian to the limb, a strategy that
will maximize the vertical resolution of our retrievals of cloud heights, haze
opacity, and gaseous ammonia concentration. With these filters and the
excellent NICMOS spatial resolution (nearly an order of magnitude improvement
over Galileo NIMS images of the northern equatorial region), we will determine
the smaller-scale structure of fresh NH3 clouds and provide cloud heights as
constraints for models of convection and dynamics associated with 5-micron
hotspots. HST is essential for this project, since no other observatory can
provide the necessary spatial resolution, and no ground-based or space-based
telescopes can observe the ammonia bands we have selected.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10162
Title:               Resolving the Thermal Conduction Front in the Bubble S308
PI:                  You-Hua Chu
PI Institution:      University of Illinois at Urbana - Champaign

Heat conduction is one of the most fundamental processes in the interstellar
and intergalactic media.  Many astronomical systems contain cool (<10^4 K) gas
in contact with hot (10^6 -10^8 K) gas;  at the contact surfaces, heat
conduction occurs and may play an essential role in the thermal structure and
evolution of the system.  Observations of thermal conduction fronts have been
extremely limited.  Conventionally observations use absorption lines of
collisionally ionized high ions as tracers of 1-3x10^5 K gas in the conduction
front.  Such observations allow the determination of column densities but not
the relative locations of these tracer ions.  Emission-line observations of a
clear-cut, edge-on conduction front are needed to study the physical structure
of a thermal conduction front.  We have identified a clean-cut, edge-on
conduction front in the circumstellar bubble S308, using XMM-Newton X-ray
observations and ground-based optical images and spectra.  We request HST STIS
spectroscopic observations of the NV and CVI emission lines in the transition
region from the hot interior gas to the cool nebular shell.  These
observations, combined with our complementary observations at optical, FUV,
and X-ray wavelength, allow us to determine the spatially-resolved temperature
profile of a thermal conduction front.  Comparisons with models further allow
us to assess the efficiency of thermal conduction.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10163
Title:               Weighing the Most Luminous Main-Sequence Star in the
                     Galaxy
PI:                  Anthony Moffat
PI Institution:      Universite de Montreal

NGC 3603 is the most massive, visible giant HII region in our Galaxy and
virtually a clone of R136, the famous supercluster in the core of the 30 Dor
region in the LMC. NGC 3603 harbors three young, extremely luminous, hot stars
which mimic the spectral appearance of WN6ha stars. As tailored atmosphere
analysis reveals, these stars are unevolved, very massive stars on the main
sequence. In fact, these stars have the potential of being the most massive
main sequence stars known in our Galaxy. One of these WN6ha stars is a double-
eclipsing binary with a 3.772(3)d period. We propose here to use HST/STIS to
carry out, for the first time, repeated, high-quality spectroscopy of this
binary in order to derive Keplerian orbits for both components and thus
directly measure their masses. Additional photometry will considerably refine
the solution for the inclination angle. Whether or not the mass of the WN6ha
(and possibly also its companion) star significantly exceeds 60 M_sol, the
current directly-observed, upper limit of main sequence stars, will allow us
to put models for massive stars to the test. As a by-product of our
observations, we will also monitor the two remaining WN6ha stars in NGC 3603.
At least one of them shows strong indications for binarity.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10164
Title:               HD 62542:  Probing the Bare, Dense Core of an
                     Interstellar Cloud
PI:                  Daniel Welty
PI Institution:      University of Chicago

The line of sight to HD 62542 is remarkable for its unusual UV extinction,
high column densities of various molecules, and apparent dearth of diffuse
atomic gas.  The main interstellar cloud appears to be a small,  dense (n_H ~
500--1000 cm^-3), molecular knot whose more diffuse outer layers have been
stripped away  by stellar winds and shocks.  As such, it provides an ideal
venue for investigating the properties of dense,  molecular gas --- with
minimal confusion from any associated diffuse gas.  We propose to obtain high
resolution, moderately high S/N STIS spectra of C I, CO and its isotopomers,
C_2, C II, O I, and many other atomic species.  Those data will be used to
compare various diagnostics of the physical conditions (e.g., C I  and O I
fine structure exciattion, CO and C_2 rotational excitation), to determine the
relative abundances of the various CO isotopomers (fractionation), and to
determine the depletions of various elements in dense  gas (the predicted
severe depletions have likely been masked by associated diffuse gas in other
cases). Understanding the fractionation and excitation of CO in this
relatively simple case will aid in understanding its  behavior in other more
complex regions (important because CO and its isotopomers are often used to
trace  and characterize molecular gas when H_2 cannot be measured).
================================================================================

Proposal Category:   GO
Scientific Category: SOLAR SYSTEM
ID:                  10165
Title:               Determination of orbits and colors for two new binaries
                     in the Koronis asteroid family
PI:                  William Merline
PI Institution:      Southwest Research Institute

We propose to measure color and orbital properties of two asteroid binaries in
the Koronis family discovered in our SNAP-9747 survey. The best previously
studied asteroid binary system, Ida/Dactyl, is also in the Koronis family.
Differential space weathering measured on the Ida and Dactyl surfaces has been
a powerful constraint on models of satellite formation mechanisms and
satellite survivability.  HST offers the unique opportunity for similar
measurements of these much smaller, main-belt binaries.  The new satellites
are believed to have formed through different collisional mechanisms than
Ida/Dactyl.  Further, with a set of 4 relative position measurements for each
of the two systems, added to the discovery snapshots, we will determine and
compare the densities of the primaries with Ida (a large, 31.5 km, asteroid
with density 2.6+-0.5 g/cm^3, measured by the Galileo flyby). In contrast,
(17246) and (22899) are 4.5 km bodies that are likely to have been
restructured since the family-forming event by subsequent collisions.  As all
are members of the same family, differences in density would constrain bulk
composition and internal structure (e.g. shard vs. rubble-pile).  Hence, these
measurements are likely to further elucidate the mechanisms for formation of
satellites.
================================================================================

Proposal Category:   GO
Scientific Category: SOLAR SYSTEM
ID:                  10166
Title:               ACS and WFPC2  Stellar Photometry in the Kepler Mission
                     Target Field
PI:                  William Borucki
PI Institution:      NASA Ames Research Center

We will observe three regions at the Galactic Equator (GE) to determine the
areal density of background stars down to apparent visual magnitude 25.
Eclipsing binary stars of this magnitude may confound Kepler photometric data,
which are intended to detect transits of Earth-size planets across foregroud
parent stars.  The GE is the region of greatest areal density of target stars,
but there is no information on the numbers of 25th magnitude stars there.  The
Kepler mission is obligated to do everything possible to avoid false positive
claims of Earth-size planets, because following missions, such as the
Terrestrial Planet Finder will rely on Kepler findings to optimize their
designs.  The proposed observations will guide the Kepler team in their
efforts to avoid false positives.  For example, the data could indicate that
it would be better for Kepler to abandon the area of greatest target
opportunity in order to reduce the risk of false positive claims.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10167
Title:               Imaging of Ices in Circumstellar Disks
PI:                  Alycia Weinberger
PI Institution:      Carnegie Institution of Washington

The link between the material of the interstellar medium and the ultimate
composition of planets lies in the way gas and dust are processed in
circumstellar disks.  Planet formation models rely upon a knowledge of the
disk constituents and temperature profiles to simulate how small grains
eventually combine into terrestrial planets and gas giant cores. Disks around
other stars may be analogs for our own early Solar System and thus allow the
direct measurement of such phenomena.  Only recently, however, have well-
resolved images of dust disks around several late T Tauri or main sequence
stars been secured.  HST provides a uniquely stable platform for making such
sensitive high dynamic range images.  Now, for those handful of disks already
resolved, we are able to go beyond the discovery phase and begin making
astrophysical measurements to deepen our understanding of the course of disk
evolution.  We therefore propose a multi-wavelength study with NICMOS designed
to discover the spatial distribution of two common Solar System materials --
methane and water ices -- in other systems.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10168
Title:               Spatially Relsoved Spectroscopy of HR 4796A's Dust Ring
PI:                  Alycia Weinberger
PI Institution:      Carnegie Institution of Washington

HST's high-contrast capabilities provide exciting imaging of circumstellar
debris disks with complex structures.  In particular, broad-band imaging using
the coronagraphs in NICMOS and STIS has elucidated the disk  morphology of HR
4796A exquisitely, but can only provide colors, not detailed compositional
information on its dust. With spectra, we will measure the detailed albedo of
the disk dust over a large wavelength range and search for interstellar
medium-like molecules and water ice.  We will also use our spatially resolved
spectra for very high angular resolution profiles of the disk width to
constrain models for planets circling inside the dust.  We have demonstrated
in a previous program how to use STIS for spatially resolved disk
spectroscopy. We now propose to use our technique to study HR 4796A.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10169
Title:               Star Formation in Luminous Infrared Galaxies: giant HII
                     Regions and Super Star Clusters
PI:                  Almudena Alonso-Herrero
PI Institution:      Instituto de Estructura de la Materia

Luminous Infrared Galaxies (LIRGs,LIR = 10^11-10^12Lsol) and Ultraluminous
Infrared Galaxies (LIR>10^12Lsol) account for approximately 75% of all the
galaxies detected in the mid-infrared in the redshift range z=0-1.5. In the
local universe it is found that LIRGs are predominantly powered by intense
star formation (SF). However, the physical conditions and processes governing
such dramatic activity over scales of tens to a few hundred parsecs are poorly
known. In the last decade HST has been playing a significant role, mainly with
the discovery of super star cluters (SSCs), and more recently, giant HII
regions. Based on observations of a few LIRGs, we found that these giant HII
regions and associated SSCs appear to be more common in LIRGs than in normal
galaxies, and may dominate the star formation activity in LIRGs. A larger
sample is required to address fundamental questions. We propose an HST/NICMOS
targeted campaign of a volume limited sample (v<5200km/s) of 24 LIRGs. This
proposal will probe the role of giant HII regions in the overall energetics of
the current star formation, their relation to SSCs, and the dependence of star
formation properties on other parameters of LIRGs. Such detailed knowledge of
the SF properties of LIRGs in the local universe is essential for
understanding galaxies at high redshift.
================================================================================

Proposal Category:   SNAP
Scientific Category: SOLAR SYSTEM
ID:                  10170
Title:               Atmospheric Variability on Uranus and Neptune
PI:                  Kathy Rages
PI Institution:      SETI Institute

We propose Snapshot observations of Uranus and Neptune to monitor changes in
their atmospheres on time scales of weeks, months, and years.  Uranus is
rapidly approaching equinox in 2007, with another 4 degrees of latitude
becoming visible every year. Recent HST observations during this epoch
(including 6818: Hammel, Lockwood, and Rages; 7885: Hammel, Karkoschka, and
Marley; 8680: Hammel, Rages, Lockwood, and Marley; and 8634: Rages, Hammel,
Lockwood, Marley, and McKay) have revealed strongly wavelength-dependent
latitudinal structure and the presence of numerous visible-wavelength cloud
features in the northern hemisphere.  Long-term ground-based observations
(Lockwood and Thompson 1999) show seasonal brightness changes whose origins
are not well understood.  Recent near-IR images of Neptune obtained using
adaptive optics on the Keck Telesccope together with images from our Cycle 9
Snapshot program (8634) show a general increase in activity at south temperate
latitudes as well as the possible development of another Great Dark Spot.
Further Snapshot observations of these two dynamic planets will elucidate the
nature of long-term changes in their zonal atmospheric bands and clarify the
processes of formation, evolution, and dissipation of discrete albedo
features.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10171
Title:               Ultraviolet Spectrum of the Binary Millisecond Pulsar
                     J0437-4715
PI:                  George Pavlov
PI Institution:      The Pennsylvania State University

PSR J0437-4715 is the nearest and the brightest millisecond (recycled) pulsar,
and the only one detected at near-optical wavelengths. We detected it with the
HST STIS/FUV-MAMA detector and found that its FUV spectrum is consistent with
being emitted from the neutron star surface with a temperature of about 0.1
MK, surprisingly high for such an old object. We also found evidence of an
emission line at 1372 A, tentatively interpreted as a Zeeman component of the
hydrogen Ly-alpha line in a magnetic field of 700 MG. Unfortunately, the
spectrum was imaged in a region of strong detector background, which strongly
hampered the spectral and timing analyses. We propose to re-observe the pulsar
with the FUV-MAMA, placing the target in a low-background region, and also
observe it with the NUV-MAMA to obtain the spectrum and pulsations in a broad
UV range. The spectral analysis will allow us to measure the temperature of
the full neutron star surface and test the origin of the heating of old
neutron stars. Confirmation of the spectral line would lead to a first direct
measuremnt of the magnetic field and radius  of a spin-powered neutron star
and uniquely constrain the equation of state of superdense matter. The NUV
spectrum and pulsations will also probe the magnetospheric emission and the
thermal structure of the cool white dwarf companion.
================================================================================

Proposal Category:   GO
Scientific Category: STAR FORMATION
ID:                  10172
Title:               Our Galaxy's most promising Super Star Cluster candidate,
                     Westerlund 1: Tip of the Iceberg?
PI:                  Richard de Grijs
PI Institution:      University of Sheffield

Recent ground-based observations have revealed that the highly reddened
Galactic cluster Westerlund 1 is the current best and by far the nearest
"Young Massive Star Cluster" (YSC) candidate, i.e. a young (< 10 Myr), dense
and massive (> 10,000 Mo) object of which until recently 30 Doradus in the LMC
was believed to be the nearest example. However, extrapolations of the locally
derived cluster luminosity function indicate that perhaps up to a hundred
similar objects should exist within the Galaxy. The close-up view of a YSC
provided by Westerlund 1 allows us to obtain an unprecedented glimpse of the
process of massive cluster formation, evolution and fate, which are among the
very key issues in modern astrophysics.  Utilising deep ACS and NICMOS imaging
and sophisticated N-body and Monte Carlo simulations, we will address key
questions regarding Westerlund 1's nature, formation and dynamical evolution.
These include, What are the initial conditions with which Westerlund 1 was
born? To what degree was mass segregation really primordial? Has the binary
fraction changed during the short cluster lifetime? Do we expect the cluster
to have a population of stellar-mass black holes? Does the cluster harbour an
intermediate-mass black hole in its core? Is Westerlund 1 unique as a Galactic
YSC? How similar is the cluster to the massive "Arches" and "Quintuplet"
Galactic Centre clusters, and to 30 Doradus?  With an expected life-span of >
100 Myr, it is conceivable that there should be more YSCs like Westerlund 1 in
the Galactic disk. Our dynamical simulations will help us determine the
ultimate fate of such clusters, allowing us to at least begin to answer the
question of Westerlund 1's uniqueness in the context of the Galaxy's stellar
populations.
================================================================================

Proposal Category:   SNAP
Scientific Category: AGN/QUASARS
ID:                  10173
Title:               Infrared Snapshots of 3CR Radio Galaxies
PI:                  William Sparks
PI Institution:      Space Telescope Science Institute

Radio galaxies are an important class of extragalactic objects:  they are one
of the most energetic astrophysical phenomena and they provide an exceptional
probe of the evolving Universe, lying typically in high density regions but
well-represented across a wide redshift range. In earlier Cycles we carried
out extensive HST observations of the 3CR sources in order to acquire a
complete and quantitative inventory of the structure, contents and evolution
of these important objects. Amongst the results, we discovered new optical
jets, dust lanes, face-on disks with optical jets, and revealed point-like
nuclei whose properties support FR-I/BL Lac unified schemes. Here, we propose
to obtain NICMOS infrared images of 3CR sources with z<0.3 as a major
enhancement to an already superb dataset. We aim to deshroud dusty galaxies,
study the underlying host galaxy free from the distorting effects of dust,
locate hidden regions of star formation and establish the physical
characteristics of the dust itself. We will measure frequency and spectral
energy distributions of point-like nuclei, expected to be stronger and more
prevelant in the IR, seek spectral turnovers in known synchrotron jets and
find new jets. We will strongly test unified AGN schemes and merge these data
with existing X-ray to radio observations. The resulting database will be an
incredibly valuable resource to the astronomical community for years to come.
================================================================================

Proposal Category:   SNAP
Scientific Category: GALAXIES
ID:                  10174
Title:               Dark-matter halos and evolution of high-z early-type
                     galaxies
PI:                  Leon Koopmans
PI Institution:      Kapteyn Astronomical Institute

Gravitational lensing and stellar dynamics provide two complementary methods
to determine the mass distribution and evolution of luminous and dark-matter
in early-type (E/S0) galaxies. The combined study of stellar dynamics and
gravitational lensing allows one to break degeneracies inherent to each method
separately, providing a clean probe of the internal structure of massive
galaxies. Since most lens galaxies are at redshifts z=0.1-1.0, they also
provide the required look-back time to study their structural and stellar-
population evolution. We recently analyzed 5 E/S0 lens galaxies between z=0.5
and 1.0, combining exquisite Hubble Space Telescope imaging data with
kinematic data from ground-based Keck spectroscopy, placing the first precise
constraints on the dark-matter mass fraction and its inner slope beyond the
local Universe. To expand the sample to ~30 systems -- required to study
potential trends and evolution in the E/S0 mass profiles -- we propose to
target the 49 E/S0 lens-galaxy candidates discovered by Bolton et al. (2004)
from the Sloan Digital Sky Survey (SDSS). With the average lens rate being 40%
and some systems having a lensing probability close to unity, we expect to
discover ~20 strong gravitational lenses from the sample. This will triple the
current sample of 9 E/S0 systems, with data in hand.  With the sample of 30
systems, we will be able to determine the average slope of the dark-matter and
total mass profile of E/S0 galaxies to 10% and 4% accuracy, respectively. If
present, we can simultaneously detect 10% evolution in the total mass slope
with 95% confidence. This will provide unprecedented constraints on E/S0
galaxies beyond the local Universe and allow a stringent test of their
formation scenarios and the standard cosmological model.
================================================================================

Proposal Category:   SNAP
Scientific Category: HOT STARS
ID:                  10175
Title:               STIS Snapshot Survey of Boron Abundances in Early-B Stars
PI:                  Charles Proffitt
PI Institution:      Catholic University of America

Boron abundances in massive stars provide a unique constraint for new
theoretical models of stellar evolution that include rotation. We propose to
use STIS to measure the B III doublet near 2066 Angstroms  in a large sample
of early-B stars. A high priority will be placed on obtaining abundances for
several stars in each of a number of different young clusters, assocations,
and star forming regions. This will allow quantitative comparision with
theoretical predictions of rotationally driven mixing in early B stars as
function of mass, age, and rotation rate. Since boron abundance measurements
are not possible for large vsin(i) values, and sin(i) is not known for
individual stars, a large sample is required to statistically test the
predictions of boron depletion as a function of the true rotation rate.
For bright nearby stars (25 targets) we will use the G230MB grating and obtain
very high S/N (>200:1).   This avoids the need for an ND filter which would
discard 99% of the photons. Spectral synthesis techniques will allow us to
derive accurate abundances despite the moderate resolution of this grating,
even for stars with relatively high vsin(i) values. This is especially
important in testing rotational models, as current abundance measurements are
mostly for stars with much lower than average rotation rates. For fainter,
more distant stars (27 targets) we will use the E230M or E230H grating with
the 0.2x0.2 aperture.
================================================================================

Proposal Category:   GO
Scientific Category: STAR FORMATION
ID:                  10176
Title:               Coronagraphic Survey for Giant Planets Around Nearby
                     Young Stars
PI:                  Inseok Song
PI Institution:      University of California - Los Angeles

A systematic imaging search for extra-solar Jovian planets is now possible
thanks to recent progress in identifying "young stars near Earth". For most of
the proposed young (<~ 30 Myrs) and nearby (<~ 60 pc) targets, we can detect a
few Jupiter-mass planets as close as a few tens of AUs from the primary stars.
This represents the first time that potential analogs of our solar system -
that is planetary systems with giant planets having semi-major axes comparable
to those of the four giant planets of the Solar System - come within the grasp
of existing instrumentation. Our proposed targets have not been observed for
planets with the Hubble Space Telescope previously. Considering the very
successful earlier NICMOS observations of low mass brown dwarfs and planetary
disks among members of the TW Hydrae Association, a fair fraction of our
targets should also turn out to posses low mass brown dwarfs, giant planets,
or dusty planetary disks because our targets are similar to (or even better
than) the TW Hydrae stars in terms of youth and proximity to Earth.  Due to
the recent cancellation of SM4, HST will inevitably degrade into a 2-gyro mode
soon and high contrast survey programs like our own cannot be carried out with
two gyros. This means that the HST cycle 13 may be the last chance to find
young Solar System analogs in the coming decade. Should HST time be awarded
and planetary mass candidates be found,  proper motion follow-up of candidate
planets will be done with ground-based AOs.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10177
Title:               Solar Systems In Formation:  A NICMOS Coronagraphic
                     Survey of Protoplanetary and Debris Disks
PI:                  Glenn Schneider
PI Institution:      University of Arizona

Until recently, despite decades of concerted effort applied to understanding
the formation processes that gave birth to our solar system, the detailed
morphology of circumstellar material that must eventually form planets has
been virtually impossible to discern.  The advent of high contrast,
coronagraphic imaging as implemented with the instruments aboard HST has
dramatically enhanced our understanding of natal planetary system formation.
Even so, only a handful of evolved  disks (~ 1 Myr and older) have been imaged
and spatially resolved in light scattered from their constituent grains.  To
elucidate the physical processes and properties in potentially planet-forming
circumstellar disks, and to understand the nature and evolution of their
grains, a larger spatially resolved and photometrically reliable sample of
such systems must be observed.  Thus, we propose a highly sensitive
circumstellar disk imaging survey of a well-defined and carefully selected
sample of YSOs (1-10 Myr T Tau and HAeBe stars) and (> app 10 Myr) main
sequence stars, to probe the posited epoch of planetary system formation, and
to provide  this critically needed imagery. Our resolved images will shed
light on the spatial distributions of the dust in these thermally emissive
disks. In combination with their long wavelength  SEDs the  physical
properties of the grains will be discerned, or constrained by our
photometrically accurate surface brightness sensitivity  limits  for faint
disks which elude detection. Our sample builds on the success of the
exploratory GTO 7233 program, using two-roll per orbit PSF-subtracted NICMOS
coronagraphy to provide the highest detection sensitivity  to the smallest
disks around bright stars which can be imaged with HST. Our sample will
discriminate between proposed evolutionary scenarios while providing a legacy
of cataloged morphologies for interpreting mid- and far-IR SEDs that the
recently launched Spitzer Space Telescope will deliver.  This project cannot
be done from the ground, and becomes untenable for HST after Cycle 13 under
the anticipated use of two-gyro pointing control mode.
================================================================================

Proposal Category:   GO
Scientific Category: STAR FORMATION
ID:                  10178
Title:               Imaging Polarimetry of Young Stellar Objects with ACS and
                     NICMOS: A study in dust grain evolution
PI:                  Dean Hines
PI Institution:      Space Science Institute

The formation of planetary systems is intimately linked to the dust population
in circumstellar disks, thus understanding dust grain evolution is essential
to advancing our understanding of how planets form. By combining (1) the high
resolution polarimetric capabilities of ACS and NICMOS, (2) powerful 3-D
radiative transfer codes, and (3) observations of objects known to span the
earliest stellar evolutionary phases, we will gain crucial insight into the
initial phases of dust grain growth: evolution away from an ISM distribution.
Fractional polarization is a strong function of wavelength, therefore by
comparing polarimetric images in the optical and infrared, we can sensitively
constrain not only the geometry and optical depth of the scattering medium,
but also the grain size distribution.  By observing objects representative of
the earliest evolutionary sequence of YSOs, we will be able to investigate how
the dust population evolves in size and distribution during the crucial
transition from a disk+envelope system to a disk+star system.  The proposed
study will help to establish the fundamental time scales for the initial
depletion of ISM-like grains: the first step in understanding the
transformation from small submicron sized dust grains, to large millimeter
sized grains, and untimely to planetary bodies.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10179
Title:               A Coordinated NICMOS and XMM Experiment to Observe the
                     Variability of Sgr A*
PI:                  Farhad Yusef-Zadeh
PI Institution:      Northwestern University

The massive black hole Sgr A* at the Galactic center has recently shown not
only quiescent emission at near-IR wavelengths, but also flare activity with
quasi-periodicity of 17 minutes. Our research group has been granted two
blocks of observing time with XMM-Newton to monitor the spectral and temporal
properties of Sgr A*. Simultaneously with these X-ray observations, we will
also monitor Sgr A* at radio, submillimeter, near-IR, and gamma-ray
wavelengths. We propose to use NICMOS in parallel with the XMM observations to
provide evidence of a well-defined minimum periodicity in the spectrum of
flare periodicities. This, combined with periodicity in the near-IR line
emission, would strengthen the claim that the emitting gas resides at the
innermost stable circular orbit around the GC black hole, thus measuring the
spin parameter of a massive black hole. Current groundbased near-IR data
suggest a spin parameter of ~0.5. In addition, the correlation pattern of
emission over a wide spectrum would elucidate a key issue of how to explain
the low luminosity of Sgr A*. The NICMOS on HST is the only instrument that
can accurately measure the 17 minute quasi-periodic variability of Sgr A*
because of the long time baseline over which HST can observe Sgr A* in
parallel with XMM-Newton.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10180
Title:               Ultracompact Blue Dwarfs: Galaxy Formation in the Local
                     Universe?
PI:                  Michael Corbin
PI Institution:      Computer Sciences Corporation

Recent observations suggest that very low-mass galaxies in the local universe
are still in the process of formation.  To investigate this issue we propose
to obtain deep ACS HRC images in the U, V and I bands of a sample of 11
"ultracompact" blue dwarf galaxies (UCBDs) identified in the Sloan Digital Sky
Survey.  These objects are nearby (z < 0.009), actively star-forming, and have
extremely small angular and physical sizes (d < 6" and D < 1 kpc).  They also
tend to reside in voids.  Our WFPC2 images of the prototype object of this
class, POX 186,  reveal this tiny object to have a highly disturbed morphlogy
indicative of a recent (within 10^8 yr) collision between two small (~ 100 pc)
clumps of stars that could represent the long-sought building blocks predicted
by the Press-Schechter model of hierarchical galaxy formation.  This collision
has also triggered the formation of a "super" star cluster (SSC) at the
object's core that may be the progenitor of a globular cluster.  POX 186 thus
appears to be a very small dwarf galaxy in the process of formation.  This
exciting discovery strongly motivates HST imaging of a full sample of UCBDs in
order to determine if they have morphologies similar to POX 186.  HST images
are essential for resolving the structure of these objects, including
establishing the presence of SSCs.  HST also offers the only way to determine
their morphologies in the near UV.  The spectra of the objects available from
the SDSS will also allow us to measure their star formation rates, dust
content and metallicities.  In addition to potentially providing the first
direct evidence of Press-Schechter building blocks, these data could yield
insight into the relationship between galaxy and globular cluster formation,
and will serve as a test of the recent  "downsizing" model of galaxy formation
in which the least massive objects are the last to form.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10181
Title:               ACS/NICMOS Imaging of Bright Lyman Break Galaxy
                     Candidates from SDSS
PI:                  Misty Bentz
PI Institution:      Ohio State University

The recent surprising discovery of six unusually bright (r~20 mag) Lyman break
galaxy (LBG) candidates with z=2.45-2.80 in the Sloan Digital Sky Survey
(SDSS) raises a number of questions that only HST can address.  Specifically,
what is the true nature of these objects, and what role if any is played by
gravitational lensing?  We propose to use the superior resolution and
sensitivity of ACS and NICMOS to obtain deep images of these objects and their
environments.  Compared to SDSS images, HST will allow us to determine their
morphologies (extended, point-source, or lensed), the appearance of their
environments (rich or poor), and to detect any faint foreground groups or
clusters that might be responsible for lensing these objects.  All outcomes
would be intruiging.  If the objects are lensed, it increases from 1 (MS1512-
cB58) to 7 the number of normal LBGs bright enough to study individually.  If
they are instead unlensed point sources, they will represent a new class of
previously unidentified absorption-line quasars.  Finally, if they are
unlensed and extended star-forming galaxies, they are at least 4mag brighter
than L_* LBGs, thus making them the most luminous star-forming objects yet
seen, representing a heretofore unknown extreme population of objects.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10182
Title:               Towards a Comprehensive  Understanding of Type Ia
                     Supernovae:  The Necessity of UV Observations
PI:                  Alex Filippenko
PI Institution:      University of California - Berkeley

Type Ia supernovae (SNe Ia) are very important to many diverse areas of
astrophysics, from the chemical evolution of galaxies to observational
cosmology which led to the discovery of dark energy and the accelerating
Universe. However, the utility of SNe Ia as cosmological probes depends on the
degree of our understanding of SN Ia physics, and various systematic effects
such as cosmic chemical evolution. At present, the progenitors of SNe Ia and
the exact explosion mechanisms are still poorly understood, as are
evolutionary effects on SN Ia peak luminosities.  Since early-time UV spectra
and light curves of nearby SNe Ia can directly address these questions, we
propose an approach consisting of two observational components: (1) Detailed
studies of two very bright, young, nearby SNe Ia with HST UV spectroscopy at
13 epochs within the first 1.5 months after discovery; and (2) studies of
correlations with luminosity for five somewhat more distant Hubble-flow SNe
Ia, for which relative luminosities can be determined with precision, using 8
epochs of HST UV spectroscopy and/or broad-band imaging.  The HST data, along
with extensive ground-based optical to near-IR observations, will be analyzed
with state-of-the-art models to probe SN Ia explosion physics and constrain
the nature of the progenitors. The results will form the basis for the next
phase of precision cosmology measurements using SNe Ia, allowing us to more
fully capitalize on the substantial past (and future) investments of time made
with HST in observations of high-redshift SNe Ia.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10183
Title:               A Deep Far-UV Search for the Interacting Binary
                     Population in M80
PI:                  Christian Knigge
PI Institution:      University of Southampton

We propose to carry out a deep, far-ultraviolet (FUV), time-resolved survey
for cataclysmic variables (CVs) and other dynamically-formed objects in the
globular cluster (GC) M80. This will include a search for FUV counterparts to
the 17 Chandra sources in our field of view, which include 2 LMXBs and 5 X-ray
selected CV candidates. Our goal is to confirm these sources as interacting
binaries and find any additional CVs below the Chandra detection limit. We
will achieve this with 6 orbits of FUV imaging with the ACS/SB, plus one
additional orbit of NUV imaging with ACS/HRC. Since crowding is not a problem
in the FUV, this will yield time-resolved FUV photometry of all blue objects
in the cluster core. Our CV census will be both deep enough to be essentially
complete and ``broad'' enough to involve all of the following CV
characteristics:  (1) UV brightness; (2) blue FUV spectral shape; (3) strong
CIV and HeII emission; (4) short time-scale ($\sim$ minutes) variability
(flickering, WD spin); (6) intermediate time-scale ($\sim$ hours) variability
(orbital variations); (7) long time-scale ($\sim$ weeks) variability (dwarf
nova eruptions).  We will thus uncover the interacting binary population in
M80. In addition, our survey will detect numerous blue stragglers and hot
white dwarfs, as well as any other blue objects in the central regions of this
cluster.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10184
Title:               A New Class of Bright Ultraviolet Variable Sources in the
                     Globular Cluster NGC 1851
PI:                  David Zurek
PI Institution:      American Museum of Natural History

Our reductions of archival STIS/FUV-MAMA data (AR9225) have discovered 13
completely unexpected and unexplained Ultraviolet bright variables. Eleven of
the variables have been identified with evolved stars (Horizontal Branch or
Asymptotic Giant Branch). The total number and nature of these systems is
completely unknown. If these variables are binaries the implication is that
the binary fraction (up to 25%) in NGC 1851 is the highest in all Galactic
globular clusters. The radial distributions of the variables and the blue
horizontal branch stars imply a common origin and perhaps an explanation of
the bi-modal morphology of the horizontal branch in the color magnitude
diagrams of globular clusters. These variables may be the tip of the iceberg
and a critical clue concerning the infamous "second parameter". We propose to
observe NGC 1851 on three occasions with the same setup as the archival data
to determine the total number and periods of the ultraviolet variables.
================================================================================

Proposal Category:   SNAP
Scientific Category: COOL STARS
ID:                  10185
Title:               When does Bipolarity Impose itself on the Extreme Mass
                     Outflows from AGB Stars?  An ACS SNAPshot Survey
PI:                  Raghvendra Sahai
PI Institution:      Jet Propulsion Laboratory

Essentially all well-characterized preplanetary nebulae (PPNe) -- objects in
transition between the AGB and planetary nebula evolutionary phases - are
bipolar, whereas the mass-loss envelopes of AGB stars are strikingly
spherical. In order to understand the processes leading to bipolar mass-
ejection, we need to know at what stage of stellar evolution does bipolarity
in the mass-loss first manifest itself? Our previous SNAPshot surveys of a
PPNe sample (with ACS & NICMOS) show that roughly half our targets observed
are resolved, with well-defined bipolar or multipolar morphologies.
Spectroscopic surveys of our sample confirm that these objects have not yet
evolved into planetary nebulae. Thus, the transformation from spherical to
aspherical geometries has already fully developed by the time these dying
stars have become preplanetary nebulae. From this new and surprising result,
we hypothesize that the transformation to bipolarity begins during the very
late AGB phase, and happens very quickly, just before, or as the stars are
evolving off the AGB.           We propose to test this hypothesis
quantitatively, through a SNAPshot imaging survey of very evolved AGB stars
which we believe are nascent preplanetary nebulae; with our target list being
drawn from published lists of AGB stars with detected heavy mass-loss (from
millimeter-wave observations). This survey is crucial for determining how and
when the bipolar geometry asserts itself. Supporting kinematic observations
using long-slit optical spectroscopy (with the Keck), millimeter and radio
interferometric observations (with OVRO, VLA & VLBA) are being undertaken. The
results from this survey (together with our previous work) will allow us to
draw general conclusions about the onset of bipolar mass-ejection during late
stellar evolution, and will provide crucial input for theories of post-AGB
stellar evolution. Our survey will produce an archival legacy of long-standing
value for future studies of dying stars.
================================================================================

Proposal Category:   SNAP
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10186
Title:               A Lyman-alpha Snapshot Survey of FBS and SBS Galaxies
PI:                  Claus Leitherer
PI Institution:      Space Telescope Science Institute

Search strategies for primeval galaxies rely on the assumption that  Lyman-
alpha can be powered by photoionization from hot stars. Theoretical models,
however, indicate that Lyman-alpha is far from being a pure recombination
line: absorption and scattering in the interstellar medium and the kinematics
of outflowing gas make firm predictions for the Lyman-alpha strength
difficult. Therefore observational tests are required. A sample of 42 galaxies
with active star formation has been selected from the First and Second
Byurakan Survey to perform such a test. The target galaxies belong to the
spectral class s1, implying they are H II galaxies, blue compact dwarfs, or
nuclear starbursts. This sample is optimized to address whether local
starbursts are strong Lyman-alpha emitters. We propose to obtain STIS G140L
spectra of the galaxies in order to detect Lyman-alpha emission with
equivalent widths larger than 5 Angstroms in this statistically significant,
homogeneous sample. We will utilize the existing, extensive body of ground-
based data to model the stellar population and make a prediction for the
Lyman-alpha emission assuming pure recombination and no radiative transfer
effects by gas and dust. Comparison with the observations will provide
constraints on such effects. The scientific goals are twofold: First, we make
an effort to understand how an apparently simple line, such as Lyman-alpha,
can be affected by radiative transfer effects and geometries in the
interstellar medium of typical star-forming regions. Second, the proposed
study will serve as an empirical test for the probability to succeed in
detecting Lyman-alpha in more distant systems. Therefore, a high-level goal of
this project is to provide guidelines for search strategies for primeval
galaxies at high redshift. This project is ideally suited for execution in
Snapshot mode.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10187
Title:               Direct imaging of the progenitors of massive, core-
                     collapse supernovae
PI:                  Stephen Smartt
PI Institution:      University of Cambridge

Modern supernovae searches in the nearby Universe are discovering large
numbers of SNe which have massive star progenitors (Types II, Ib and Ic). The
extensive HST image archives of galaxies within ~20Mpc enables their
individual bright stellar content to be resolved. As massive, evolved stars
are the most luminous single objects in a galaxy, the progenitors of core-
collapse SNe should be directly detectable on pre-explosion images. In our
ongoing HST programme we have detected the first red supergiant progenitor of
a normal type II supernova, shown that SN 1993J came from a binary system, and
set direct mass-limits on three other type II supernovae progenitors. These
discoveries are providing strong constraints on theoretical models of pre-
supernova stellar evolution that predict which stars produce which type of
supernovae. We request time to continue this successful project, and require
ACS observations of future SNe which are discovered in galaxies closer than
20Mpc which have pre-explosion HST archive images available. These
observations will allow the SNe to be precisely positioned on the pre-
explosion frames with the required astrometric accuracy of around 0.05", and
provide 3-colour photometry of the surrounding stellar populations for
reddening estimations. The goal of this project is to directly identify the
progenitor stars of core-collapse supernovae. We will compare the results to
our own stellar evolutionary tracks in order to determine masses or
restrictive mass-limits for the progenitors.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10188
Title:               In-Depth Study of The Antennae with NICMOS and ACS
PI:                  Bradley Whitmore
PI Institution:      Space Telescope Science Institute

We propose new observations  of  "The Antennae" (NGC 4038/39), the nearest and
youngest example of a major disk-disk merger, with NICMOS and ACS.  The long
overdue NICMOS observations will allow us to penetrate the dust in the Overlap
Region, measure the P_alpha emission and CO band strengths of young clusters,
and study supernova remnants in heavily obscured regions using [FeII] images.
The high resolution  (0.05" pixel) ACS observations will allow us for the
first time to reliably distinguish clusters from stars based on their apparent
sizes, and to potentially identify hundreds of supernova remnants  that may
control the energy balance and feedback mechanisms within the ISM (based on
[SII] images).  In conjunction with our previous WFPC2, GHRS, and STIS
observations, the new data will provide answers to fundamental questions such
as: How do these clusters form and evolve? How quickly are they destroyed and
what fraction of the field stars were formed in clusters. How many clusters
are hidden by dust?   How do the clusters  and associated supernovae affect
the local and global ISM? What are the dynamical masses of the clusters, and
are the stellar IMF's  truncated?  Simultaneous parallel observations will
also determine whether clusters can form in the more quiescent environment of
the inner tails. A better understanding of how mergers form tremendous numbers
of clusters and stars in the local universe will help shed light on processes
that are crucial during galaxy assembly throughout the observable universe.
================================================================================

Proposal Category:   GO
Scientific Category: COSMOLOGY
ID:                  10189
Title:               PANS-Probing Acceleration Now with Supernovae
PI:                  Adam Riess
PI Institution:      Space Telescope Science Institute

Type Ia supernovae (SNe Ia) provide the most direct evidence for an
accelerating Universe, a result widely attributed to dark energy. Using HST in
Cycle 11 we extended the Hubble diagram with 6 of the 7 highest-redshift SNe
Ia known, all at z>1.25, providing conclusive evidence of an earlier epoch of
cosmic deceleration.  The full sample of 16 new SNe Ia match the cosmic
concordance model and are inconsistent with a simple model of evolution or
dust as alternatives to dark energy.  Understanding dark energy may be the
biggest current challenge to cosmology and particle physics.  To understand
the nature of dark energy, we seek to measure its two most fundamental
properties: its evolution (i.e., dw/dz), and its recent equation of state
(i.e., w(z=0)).  SNe Ia at z>1, beyond the reach of the ground but squarely
within the reach of HST with ACS, are crucial to break the degeneracy in the
measurements of these two basic aspects of dark energy. The SNe Ia we have
discovered and measured with HST in Cycle 11, now double the precision of our
knowledge of both properties.  Here we propose to quadruple the sample of SNe
Ia at z>1 in the next two cycles, complementing on-going surveys from the
ground at z<1, and again doubling the precision of dark energy constraints.
Should the current best fit model prove to be the correct one, the precision
expected from the current proposal will suffice to rule out a cosmological
constant at the 99% confidence level. Whatever the result,  these objects will
provide the basis with which to extend our empirical knowledge of this newly
discovered and dominant component of the Universe, and will remain one of the
most significant legacies of HST. In addition, our survey and follow-up data
will greatly enhance the value of the archival data within the target Treasury
fields for galaxy studies.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10190
Title:               The Star Formation History and Metallicity Evolution of
                     M33: A Comprehensive Study of Disk Evolution
PI:                  Donald Garnett
PI Institution:      University of Arizona

We will obtain deep, panchromatic imaging photometry of stellar populations in
four fields ranging from 0.5 to 4 scale lengths across the disk of the Local
Group spiral M33. The observations are designed to detect the oldest main-
sequence turnoffs in three outer disk fields, and to reach the crowding limit
in the innermost field. We will combine the photometry data with information
we already have in-hand on abundances from stars and H II regions in M33 to
derive the star formation history and metallicity evolution of the M33 disk.
The information  from our four fields will allow us to obtain (1) the ages of
the oldest disk stars and the radial variation of their ages; (2) the radial
variation of the star formation history and its nature (e.g., constant,
declining, or bursting); and (3) the metallicity distribution in each field
and the time evolution of the metallicity gradient.  Our team, an experienced
mix of photometrists, spectroscopists, and galaxy evolution theorists, will
use the results from this program to construct a comprehensive chemo-dynamical
model for the M33 disk. This detailed study of M33 will be a key in developing
an understanding of the formation and evolution of disks that can be applied
to studies of disks at both low and high redshift, and will also yield a
wealth of information on stellar populations, chemical evolution, and star
clusters that will be of great value to future investigators.
================================================================================

Proposal Category:   GO
Scientific Category: AGN/QUASARS
ID:                  10191
Title:               A Fundamental Test of Accretion Physics with NGC 4203
PI:                  Joseph Shields
PI Institution:      Ohio University

The rapid evolution of quasars indicates that supermassive black holes in
galaxy nuclei spend most of their time in a relatively quiescent state.
Studies of nearby galaxies demonstrate that many such black holes are
accreting at a low rate, and appear as low-luminosity active galactic nuclei
(LLAGNs).  Theoretical arguments suggest that the mode of accretion onto a
central black hole may be very different in LLAGNs as compared to high-
luminosity systems.  The LINER NGC 4203 provides an excellent opportunity to
investigate quantitatively the accretion process in a LLAGN, and hence the
typical accretion state for a supermassive black hole.  Cycle 7 STIS data
acquired at one position angle reveal double-peaked H-alpha emission in the
nucleus that may trace an accretion disk, and spatially resolved emission that
places an upper limit on black-hole mass.  We propose observations with STIS
to map the two-dimensional velocity field of the circumnuclear gas disk in the
central  regions of NGC 4203, in order to measure the black-hole mass.  This
parameter is essential for testing theoretical models of accretion,
determining the mass accretion rate, and estimating the radiative efficiency
for accreted matter.  The results will be important for making sense of
LLAGNs, and for translating their measured luminosity into accretion rates
that trace the growth of black holes.
================================================================================

Proposal Category:   GO
Scientific Category: SOLAR SYSTEM
ID:                  10192
Title:               Jupiter's Upper Stratospheric Hazes Probed with Ganymede
PI:                  Erich Karkoschka
PI Institution:      University of Arizona

I propose to observe a disappearance of Ganymede behind the dark limb of
Jupiter with five filters of the ACS/HRC camera.  Two exposures in each filter
can be taken during such an event.  The images will provide the spectral
variation of the altitude of the apparent limb of Jupiter.  The altitude of
the apparent limb is dependent on the presence of hazes in Jupiter's
stratosphere.  Hazes of vertical optical depths below 0.001 could be detected
with these observations, providing an extremely sensitive probe of high hazes.
The observations probe altitudes levels near the 1-mb pressure level, for
which we have very limited data. The creation of aerosols, their growth, and
their transport by winds is currently a mostly theoretical study.  It would
significantly benefit from constraints derived from the proposed observations.
ACS/HRC is the only instrument capable of the required spatial resolution in
the ultraviolet.  Furthermore, a favorable geometry of Ganymede's orbit occurs
only once every six years.  This proposal achieves unique results with a
minimum of HST time.
================================================================================

Proposal Category:   GO
Scientific Category: AGN/QUASARS
ID:                  10193
Title:               Can Narrow-Line Regions in Luminous AGN be Enormously
                     Large?
PI:                  Hagai Netzer
PI Institution:      Tel Aviv University - Wise Observatory

We propose to obtain long-slit optical spectra of three nearby quasars with
the largest reported narrow-line regions (NLRs). These sources have been shown
to be the cornerstone of a most interesting size--luminosity relationship in
AGN-NLRs which, we suspect, is very problematic. A two-orbit HST/STIS
observation, per source, will allow us to measure several narrow emission
lines from H_beta through H_alpha and [S II] at several distances along the
spatial direction. We will thus be able to classify the line excitation
mechanism, estimate the gas density as a function of distance from the center,
and more properly define the 'NLR size'. This will allow us to test the idea
that the NLR conditions in these quasars are very different from those
observed in low luminosity AGN and, specifically, that some of the narrow
emission lines have a star forming origin. Together with our IR spectra of
high-redshift quasars, we will be able to test the newly discovered NLR size-
luminosity relationship in AGN and the AGN-starburst connection at the high
luminosity end.
================================================================================

Proposal Category:   SNAP
Scientific Category: HOT STARS
ID:                  10194
Title:               Towards a global understanding of accretion physics -
                     Clues from an UV spectroscopic survey of Cataclysmic
                     Variables
PI:                  Boris Gaensicke
PI Institution:      The University of Warwick

Accretion inflows and outflows are fundamental phenomena in a wide variety of
astrophysical environments, such as Young Stellar Objects, galactic binaries,
and AGN. Observationally, cataclysmic variables (CVs), interacting white
dwarf/main sequence binaries, are particularly well suited for the study of
accretion processes. Furthermore, CVs that are born with a donor more massive
than the white dwarf are potential progenitors of supernovae type Ia. We are
currently carrying out a STIS UV spectroscopic snapshot survey of CVs to fully
exploit the diagnostic potential of these objects for our understanding of
accretion physics. We analyze the STIS spectra with state-of-the-art accretion
disc model spectra (SYNSPEC), testing our current knowledge of accretion disk
structure, and thereby, providing new insight into the currently poorly
understood process of viscous dissipation. In addition, we use our
parameterised wind model PYTHON for the analysis of the radiation driven
accretion disc wind spectra, assessing the fundamental question whether the
mass loss rate correlates with the disc luminosity. Our survey data also
identify a number of systems in which the white dwarf significantly
contributes to the UV flux, permitting an analysis of the impact of mass
accretion on the evolution of these compact stars. Finally, anomalous N/C
emission line flux ratios unmistakably identify CVs that started out with a
donor more massive than the white dwarf but failed to reach the Chandrasekhar
limit.  Determining the number of these "failed SNIa" will provide crucial
input for the population models of this type of system, and, consequently,
improve the predictions on the number of white dwarf binaries that actually do
overcome the Chandrasekhar limit. While the data obtained so far are of
excellent quality, the number of targets that have been observed so far is too
small for a statistically significant analysis. We propose here to extend this
survey into Cycle 13, building a homogenous database of accretion disc and
wind outflow spectra covering a wide range of mass transfer rates and binary
inclinations, and sampling the N/C abundances of at least 100 CVs.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10195
Title:               Probing the Surroundings of a Highly Luminous Redshift
                     6.5 Galaxy
PI:                  James Rhoads
PI Institution:      Space Telescope Science Institute

We propose deep images of a recently discovered galaxy at z=6.535, which is
among the most luminous Lyman-alpha emitting galaxies known at high redshift.
The brightness and rarity of this source imply that it is associated with a
high peak in the matter density distribution.  (It is the brightest Lyman
alpha source in 2e5 comoving Mpc3, with a luminosity of 6 L*.)  Further
objects in this peak are expected to be visible with HST's sensitivity.  The
Lyman alpha line has a large rest frame equivalent width, with a lower bound
>100 Angstroms.  Such a large equivalent width would be impossible  for
objects embedded in neutral gas, and instead requires either that (a) the
universe was reionized before z=6.5 or (b) the galaxy resides in a local
ionized bubble, in which case an additional contribution to the ionizing
photon budget from presently undetected neighbors is required.  With 19 orbits
of ACS and NICMOS imaging, we will measure this object's morphology and
spectral  energy distribution, thus searching for either active nuclei or old
stellar populations.  We will also search for possible neighbors, which could
establish the first known galaxy group at z>6, and may provide sufficient
ionizing flux to allow the escape of the observed Lyman alpha photons in a
neutral universe.  If neighbors are not found, it will lead to an upper bound
on the neutral fraction in the general IGM at z=6.5.
================================================================================

Proposal Category:   GO
Scientific Category: COSMOLOGY
ID:                  10196
Title:               Morphologies of a new class of rest-frame optical
                     selected high redshift galaxies
PI:                  Marijn Franx
PI Institution:      Universiteit Leiden

We have obtained deep very Js, H, Ks imaging with the VLT of two fields with
excellent optical imaging, in order to study high redshift galaxies. Using
these Near-IR images, we identified a class of galaxies with Js - Ks color
larger than 2.3. Photometric redshifts and spectroscopic follow-up showed that
their mean redshift is 2.5 +- 0.7. These galaxies are complementary to Lyman
break selected galaxies: the overlap is minimal, and the rest-frame optical
colors of the Js-Ks selected galaxies are much redder. Their contribution to
the stellar mass density is comparable to that of Lyman breaks in our fields.
SED fits and Near-IR spectroscopy of the Js-Ks selected galaxies indicate
median ages between 1 and 2 Gyr, a factor of 3-5 older than the ages of Lyman
break galaxies estimated by similar methods. They are likely the oldest
galaxies at z=2.5, and may be  evolving into the most massive galaxies at z=0.
We propose to obtain images of the spectroscopically confirmed Js-Ks galaxies
with the NICMOS/NIC3 camera in the H band. These galaxies lie the field of
MS1054-03, for which we have excellent groundbased and HST optical imaging.
The increased depth and spatial resolution of the NICMOS imaging will allow us
to determine the restframe optical morphologies of the Js - Ks galaxies, in
order to study their intensity profiles and regularity, to decompose the
largest galaxies in bulges and disks, to measure scale lengths, and to look
for evidence of merging and recent star formation. This study would provide us
unique insight into the nature of these red galaxies, their evolutionary
history and their likely descendants at low redshift.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10197
Title:               The Astrophysical Parameters of Very Metal-Poor Halo
                     Binaries
PI:                  Elliott Horch
PI Institution:      University of Massachusetts Dartmouth

Little is currently known concerning the mass-luminosity relation (MLR) of
Population II stars. In Cycle 10, we began an initial study with FGS1 to
resolve a sample of known spectroscopic binaries preselected as high-velocity
and/or low metallicity objects. This has resulted in significant new
information about the astrophysical parameters of metal-poor stars, but was
limited mainly to intermediate metallicities, not to true Population II stars.
A new sample of metal-poor spectroscopic binaries identified by Latham and his
collaborators (e.g. Latham et al 2002) contains three new very metal-poor
objects resolvable with FGS. We propose to observe these binaries and obtain
additional observations of two very important resolved targets from our
initial sample.  As with that program, we will couple the already-known
spectroscopic orbits with astrometric information which only FGS can deliver
at present. To ensure that the most will be gained from these data, we also
request observations of three metal-poor single stars to be used as
calibration objects. In combination with results from our previous program,
these observations can be expected to resolve the question of the location of
the Population II main sequence and give valuable insight into the accuracy of
isochrone fitting for determination of globular clusters ages. Due to the
combination of target magnitudes and expected separations, no object in this
sample can be resolved without the unique capabilities of FGS.
================================================================================

Proposal Category:   SNAP
Scientific Category: STELLAR POPULATIONS
ID:                  10198
Title:               Probing the Dynamics of the Galactic Bar through the
                     Kinematics of Microlensed Stars
PI:                  Przemyslaw Wozniak
PI Institution:      Los Alamos National Laboratory

The observed optical depths to microlensing of stars in the Galactic bulge are
difficult to reconcile with our present understanding of Galactic dynamics.
The main source of uncertainty in those comparisons is now shifting from
microlensing measurements to the dynamical models of the Galactic bar. We
propose to constrain the Galactic bar models with proper motion observations
of Bulge stars that underwent microlensing by determining both the kinematic
identity of the microlensed sources and the importance of streaming motions.
The lensed stars are typically farther than randomly selected stars.
Therefore, our proper motion determinations for 36 targeted MACHO events will
provide valuable constraints on the dynamics of bulge stars as a function of
distance. The first epoch data for our proposed events is already available in
the HST archive so the project can be completed within a single HST cycle. The
exceptional spatial resolution of HST is essential for completion of the
project. Constraints on the total mass in the bulge will ultimately lead to
the determination of the amount of dark matter in inner Galaxy.
================================================================================

Proposal Category:   SNAP
Scientific Category: GALAXIES
ID:                  10199
Title:               The Most Massive Galaxies in the Universe: Double
                     Trouble?
PI:                  Mariangela Bernardi
PI Institution:      Carnegie Mellon University

We are proposing an HST snapshot survey of 70 objects with velocity dispersion
larger than 350 km/s, selected from the Sloan Digital Sky Survey. Potentially
this sample contains the most massive galaxies in the Universe. Some of these
objects may be superpositions; HST imaging is the key to determining if they
are single and massive or if they are two objects in projection. The objects
which HST imaging shows to be single objects are interesting because they
potentially harbor the most massive black holes, and because their existence
places strong constraints on galaxy formation models. When combined with
ground based data already in hand, the objects which HST imaging shows are
superpositions provide valuable information about interaction rates of  early-
type galaxies as well as their dust content.  They also constrain the allowed
parameter space for models of binary gravitational lenses (such models are
currently invoked to explain discrepancies in the distribution of lensed image
flux ratios and separations).
================================================================================

Proposal Category:   GO
Scientific Category: COSMOLOGY
ID:                  10200
Title:               Dark Matter Constraints from the Merging Cluster 1E0657-
                     56
PI:                  Christine Jones
PI Institution:      Smithsonian Institution Astrophysical Observatory

We propose five orbits of ACS Wide Field Camera observations (three orbits
with F814W, one with F606W, and one with F435W) to investigate the unique,
high velocity merging cluster 1E0657-56 (z=0.296). Coupling the ACS images
with deep Chandra observations and ground-based imaging will allow us to
compare maps of the intracluster medium, the dark matter, and the galaxies
from which we can directly estimate the self-interaction cross-section of dark
matter, the dominant mass component in clusters and the Universe. These
observations, combined with hydrodynamic simulations, will either rule out the
range of cross-sections proposed to alleviate problems with collisionless dark
matter or unambiguously detect and measure the self-interaction cross-section.
A secondary objective is to quantify the impact of a supersonic merger on star
formation and the morphological evolution of cluster galaxies. The geometry of
1E0657-56 (with the merger nearly in the plane of the sky) coupled with the
subcluster velocity (4500 km/s) accurately constrains the timescale of this
merger. In particular since the subcluster traversed the dense core of the
main cluster only 0.15 Gyr ago, star formation induced by the core passage
will be clearly visible.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10201
Title:               The Origin of Dwarf Galaxies and Steep Luminosity
                     Functions in Clusters
PI:                  Christopher Conselice
PI Institution:      California Institute of Technology

Clusters of galaxies contain an overdensity of dwarfs compared to the field.
The origin of these dwarfs is unknown, but a large fraction of them did not
form through standard collapses early in the universe.  Some dwarf ellipticals
in clusters have metal rich and young stellar populations while others contain
old metal poor populations, suggesting multiple formation mechanisms and time
scales.  We propose to test the idea that dwarfs descend from galaxies
accreted into clusters during the past 8 Gyrs by correlating ages and
metallicities of dwarfs with their internal structures - spiral arms, bars,
and disks.  If dwarfs originate from more massive galaxies then these features
should be common in metal rich and young dwarfs. On the other hand, if no
correlation is found it would suggest that dwarfs form through in-situ
collapses of gas in the intragalactic medium after the universe was reionized.
================================================================================

Proposal Category:   SNAP
Scientific Category: HOT STARS
ID:                  10202
Title:               Resolving OB Binaries in the Carina Nebula, Resuming the
                     Survey
PI:                  Edmund Nelan
PI Institution:      Space Telescope Science Institute

In March 2002 we carried out a small, high-angular resolution survey of some
of the brightest OB stars in the Carina Nebula with FGS1r in an attempt to
resolve binary systems which had thus far evaded detection by other
techniques. Of 23 stars observed, 5 new OB binaries were discovered with
component separations ranging from 0.015" to0.325". This yield over the
spatial domain of FGS1r's angular resolution, coupled with published
statistics of the incidence of OB stars in short-period spectroscopic, and
long-period visual binaries suggests that the fraction of binarity or
multiplicity among OB stars is near unity. Our unexpected resolution of the
prototype O2 If* star HD 93129A as a 55 milli-arcsecond double is a case in
point that great care must be excerised when one attemps to establish the IMF
and upper-mass cuttoff at the high-mass end of the HR diagram. We propose to
resume the survey  to observe a larger, statistically meaningful sample of OB
stars to establish a firm assessment of multiplicity at the high-mass end of
the IMF in these clusters. We will also investigate the single-star/binary-
star status of several astrophysically important, individual stars in order to
enable a better understanding of the evolution of high-mass stars.
================================================================================

Proposal Category:   GO
Scientific Category: COOL STARS
ID:                  10203
Title:               The Deep Lamp Project
PI:                  Thomas Ayres
PI Institution:      University of Colorado at Boulder

Space Telescope Imaging Spectrograph is the most sophisticated space-borne
spectrometer ever built, probably the last of its kind for some time to come.
A key virtue of STIS is that its medium- and high-resolution echelle modes
provide access to broad intervals of the vacuum ultraviolet spectrum in a
single shot.  Another virtue is the validation of the wavelength scales by
periodic observations of an onboard hollow-cathode emission line source. Tying
together the different echelle orders by means of the accurately known lamp
spectrum enables a wide range of studies that exploit differential comparisons
of velocity diagnostics in stellar, interstellar, and even extragalactic
spectra.  Despite the importance of the wavelength calibrations, however, they
are done only infrequently (once a year).  While STIS undoubtedly must be one
of the most stable orbiting spectrographs ever designed, possible thermal
distortions of the instrument might cause small nonlinear deviations of the
wavelength scales and thereby impact the velocity precision.  The existing
wavecal data sets are separated too far apart in time to isolate short-term
thermal fluctuations from long-term secular behavior, and the routine
WAVELINEs taken with every grating switch are too underexposed to reveal any
differential behavior across the spectrum, aside from a simple zero-point
offset.  I therefore propose to obtain a series of deep lamp exposures in a
few representative modes of the NUV and FUV MAMAs to search for and
characterize short-term differential distortions of the echelle formats.  This
work also will provide an important dataset to test new approaches to derive
the basic dispersion relations, such as the effort underway by the Physical
Modeling Group at ESA's ST-ECF.  The calibration campaign can be scheduled in
pure parallel mode with no loss of orbits from the Cycle 13 science program.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10204
Title:               Evolution of Light Echoes of SN 1993J
PI:                  Ben Sugerman
PI Institution:      Space Telescope Science Institute

SN 1993J is the nearest SN in the last decade, and only one of seven objects
to produce confirmed light echoes.  Our analyses of archival HST/WFPC2
datareve aled that the SN has illuminated at least two light-echo structures
in the galaxy M81.  Those echoes appear to define two sheets of dust, located
roughly 260 ly and 770 ly in front of the SN, which are the first, and most
efficient, 3-D probes of the ISM in M81.  The echoes not only reveal the ISM's
structure, but also constrain the density, composition and grain-size of its
dust.  Echoes are transient events, and as they change on timescales shorter
than a year, continued monitoring will reveal new illuminated material,
tracing interstellar and circumstellar structure.  We propose a modest and
highly efficient campaign by HST to image these and yet undiscovered echoes
toward SN 1993J.  Such observations will build the first direct 3-D map of the
ISM within a million cubic parsecs of M81's spiral arm, and may glimpse the
circumstellar environment affected by the projenitor's mass loss.  Such
results probe the nature of extragalactic dust, reveal spatio-kinematic
information about the M81's disk, tightly constrain its internal extinction,
and under the proper circumstances, provide an independent distance
measurement to the host galaxy.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10205
Title:               Critical STIS Spectroscopy and ACS Imagery at the Top of
                     the IMF
PI:                  Nolan Walborn
PI Institution:      Space Telescope Science Institute

We shall observe two key massive hot stars to investigate the effects of
multiplicity and rotational mixing on their parameters and evolution.  (1) The
prototype O2 If* star HD 93129A dominates the compact cluster Trumpler 14, one
of the ionizing clusters of the Carina Nebula.  It has been an anchor point
for analyses of the most massive stars.  Unexpectedly, it has been resolved as
a 55 mas binary by FGS.  The derived delta m of 0.9 implies that the companion
may be similar to the O3 dwarfs HD 93128 and HD 93129B (3" from A) in Tr 14.
Recent radio and X-ray data suggest that the HD 93129A system is a colliding-
wind binary.  We propose to resolve the system spectroscopically with STIS in
both the optical and FUV.  Also, we plan an orbit of very short ACS exposures
on this key cluster to obtain resolved multicolor photometry of its crowded
inner members for the first time.  (2) The recent discovery of a CNO dichotomy
among five O2 giants in the Magellanic Clouds provides a new evolutionary
diagnostic for the most massive stars, which is related to their initial
rotational velocities.   The abundance anomalies are seen in the UV wind
spectra as well as optical lines.  We propose to observe the FUV spectrum of
the LMC ON2 star LH10-3061 with STIS to support further analysis, since it is
the only one of these stars lacking UV data.
================================================================================

Proposal Category:   GO
Scientific Category: AGN/QUASARS
ID:                  10206
Title:               What drives the outflows in powerful radio galaxies?
PI:                  Clive Tadhunter
PI Institution:      University of Sheffield

There is increasing speculation that activity-induced outflows are an
important feedback  mechanism in evolution of galaxy bulges, yet uncertainties
remain about the nature, dominant  driving mechanism and powers of the
outflows. In order to address these issues, we propose  to make deep ACS and
STIS observations of two compact radio sources in which we recently  found
unequivocal evidence for powerful emission line outflows, and in which all the
potential  drivers for the outflows -- quasar nuclei, relativistic jets and
starbursts -- are known to be  present. Using the unique capabilities of
HST/ACS we will map the outflow regions in these  sources at high spatial
resolution and thereby determine the dominant outflow driving mechanism.  In
addition, by combining the morphological information from the ACS data with
information  on the kinematics and physical conditions derived from STIS and
ground-based spectra, we  will determine the mass outflow rates and powers in
the outflows. This will be the first  comprehensive study of the near-nuclear
outflows in radio galaxies. Such studies  are crucial for determining whether
the activity associated with powerful extragalactic radio sources has a major
impact on the evolution of the host early-type galaxies.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10207
Title:               Star Formation in Damped Lya Galaxies: Testing the
                     Connection with the Lyman Break Population
PI:                  Jason Prochaska
PI Institution:      University of California - Santa Cruz

The principal challenge of damped Lya (DLA) research is to identify and study
the stellar components of these galaxies. Although two decades of absorption-
line research has yielded the HI gas content, metallicity, velocity fields,
molecular and dust content of these galaxies only a handful have been studied
in emission.    Therefore, it has been very difficult to compare the DLA
galaxies with the successful surveys of high z galaxies discovered in emission
(e.g. Lyman break galaxies; LBG).  This is particulary important given that
DLA systems are the probable precursors to galaxies like the Milky Way.
Because the DLA systems are identified toward bright background quasars, deep
observations at high spatial resolution with astable PSF are essential and
only HST provides the observing capability.      Recently, two major advances
have greatly enhanced the prospects for measuring emission from DLA host
galaxies: (1) we have developed a new spectroscopic technique for inferring
the star formation rates (SFR) of the DLA which enables one to pre-select the
brightest candidates; (2) the high spatial resolution of the ACS represents a
major improvement over previous capabilities. We will obtain deep V-band
images with the HRC+ACS of 8 high z DLA with the highest inferred apparent UV
magnitudes.  The complete survey will offer a robust satistical analysis of:
(a) the extent and morphology of the  DLA star forming regions; (b) the
likelihood that the DLA and LBG correspond to the same population of
protogalaxies; (c) a test of the protogalactic clump models favored by CDM
cosmology.  We emphasize this program will offer a major advance over all
previous studies.  Finally, we will complement these HST observations with an
extensive observing campaign (IFU spectroscopy and deep IR imaging) on the
Keck, VLT, and Magellan telescopes to provide the most extensive dataset yet
on the physical properties of high z DLA.
================================================================================

Proposal Category:   GO
Scientific Category: COOL STARS
ID:                  10208
Title:               NICMOS Differential Imaging Search for Planetary Mass
                     Companions to Nearby Young Brown Dwarfs
PI:                  Wolfgang Brandner
PI Institution:      Max-Planck-Institut fur Astronomie, Heidelberg

We propose to use the differential spectral imaging capability of HST/NICMOS
(NIC1) to search for planetary mass companions. We target the twelve most
nearby (within 30 pc), isolated (no known close companion), and young (< 1Gyr)
brown dwarfs. All of them have spectral type L and show signs of Lithium
absorption, which clearly proves their substellar nature and youth. Planetary
mass companions with masses down to 6 Jupiter masses, and at separations
larger than 3 A.U. are bright enough for a direct detection with HST/NICMOS
using the spectral differential imaging technique in two narrow-band filters
placed on and off molecular bands. The proposed project has the potential to
lead to the first direct detection of a planetary mass object in orbit around
a nearby brown dwarf.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10209
Title:               On the evolutionary status of extremely hot helium stars
                     - are the O(He) stars successors of the RCrB stars?
PI:                  Thomas Rauch
PI Institution:      Universitat Erlangen-Nurnberg

We propose UV spectroscopy of the four unique post-AGB stars of spectral type
O(He) in order to understand the origin of their peculiar surface abundances.
These stars are the only known amongst the hottest post-AGB stars (effective
temperatures > 100,000 K) whose atmospheres are composed of almost pure
helium. This chemistry markedly differs from that of the hydrogen-deficient
post-AGB evolutionary sequence with objects which have carbon dominated
atmospheres (PG1159 stars and Wolf-Rayet central stars).  While PG1159 and
Wolf-Rayet stars are the result of a late helium-shell flash, this scenario
cannot explain the O(He) stars. Instead, they are possibly double-degenerate
mergers. We speculate that the four O(He) stars represent evolved RCrB stars,
which also have helium dominated atmospheres. We aim to determine the C, N, O,
and Si abundances precisely, in order to proof this evolutionary link.
================================================================================

Proposal Category:   GO
Scientific Category: COSMOLOGY
ID:                  10210
Title:               Groups of Dwarf Galaxies: Pools of Mostly Dark Matter?
PI:                  R. Tully
PI Institution:      University of Hawaii

Within 5 Mpc, there are 6 groups with well-known luminous galaxies but there
also appears to be a comparable number of groups containing only dwarfs.  If
these dwarf entities are truly bound then M/L values are an order of magnitude
higher than values found for groups with luminous spiral galaxies.  There are
theoretical reasons to anticipate that low mass halos may frequently be mostly
dark.  The dynamical influence of low mass halos is negligible in familiar
groups with luminous members.  By contrast, a study of the dynamics of `groups
of dwarfs' may provide direct evidence of the existence of dark matter
potential wells with few baryons.  The goal of the present study is to gather
detailed information on the 3-D distribution of dwarf galaxies suspected to
lie within 7 groups of dwarfs within 5 Mpc.  Distances with 7% relative
accuracy can be measured with the Tip of the Giant Branch method with ACS and
integrations within 1 orbit per target.
================================================================================

Proposal Category:   GO
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID:                  10211
Title:               A Combined HST/Chandra Study for Finding the Baryons in
                     the Low Redshift Universe.
PI:                  Smita Mathur
PI Institution:      Ohio State University

The main reservoir of low redshift baryons is still ``missing'': all the
observed stellar and gaseous components add up to a factor of ten below the
abundance predicted by big bang nucleosynthesis. Hydrodynamic cosmological
simulations predict that a large fraction of the low redshift baryons should
reside in a warm/hot diffuse intergalactic medium (IGM), detectable via an
``X-ray forest'' of high excitation metal lines, but blind searches of X-ray
lines are extraordinarily difficult with present technology. A first hint of
this warm-hot IGM may have been found in recent studies of OVI absorption
towards background quasars.  However, the significance of OVI  absorbers to
the total baryon budget is uncertain and UV observations alone cannot
determine the physical conditions in the IGM. We propose STIS/E140M
observations to search for intervening OVI absorbers towards two quasars that
are bright enough in X-rays for follow-up Chandra spectroscopy. The combined
UV/X-ray study provides a powerful tool to (1) assess the cosmological
significance of OVI absorbers; (2) determine their physical properties using
OVII/OVI and OVIII/OVI ratios; and (3) pursue detection and study of the warm-
hot IGM.
================================================================================

Proposal Category:   GO
Scientific Category: COOL STARS
ID:                  10212
Title:               A Critical Test for Radiatively Driven Hot Winds in Cool
                     Stars
PI:                  Alex Lobel
PI Institution:      Harvard University

We propose STIS observations of the C IV resonance emission line profiles for
the two brightest short-period classical Cepheid variables Delta Cep and Beta
Dor, to critically test if P Cygni-type profiles form in the hot transition
region plasmas of their pulsating upper atmospheres. Recent FUSE observations
of the cool (non-variable) G-supergiant Alpha Aqr (and Beta Aqr) show a
distinct P Cygni-type profile in warm transition region emission lines of C
III. The observations reveal supersonic wind outflow velocities that exceed
~140 km/s, based on our semi-empiric radiative transfer models. The models
demonstrate that optically thick supersonic winds occur in the outer
atmospheres of cool giant and supergiant stars, at kinetic gas temperatures
well above 80 kK.  STIS observations of cool regular pulsating Cepheid
variables will confirm or reject our present hypothesis that these peculiar P
Cygni-type line shapes form in a supersonic accelerating wind structure that
is (partly) driven by a radiative atmospheric acceleration mechanism,
generally adopted for driving the much faster winds of hot luminous stars.
STIS observations of the detailed line shapes of hot transition region
emission lines in Cepheids can establish an important physical link between
the radiation-driven wind theory of hot stars, and the acoustic/magnetic wave-
driven wind theory of cool stars. The proposed high-resolution far-UV spectra
of these important pulsating cool stars will be an invaluable contribution to
the HST Archive.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10213
Title:               Optical identification of two nearby Isolated Neutron
                     Stars through proper motion measuremnt.
PI:                  Silvia Zane
PI Institution:      Mullard Space Science Laboratory

Aim of   this   proposal is    to  perform  high-resolution    imaging of the
proposed optical counterparts   of the two, radio  silent,   isolated
neutron  stars   RXJ1308.6+2127 and     RX J1605.3+3249 with  the STIS/50CCD.
Imaging both  fields with the same instrumental configuration used  in mid
2001  by Kaplan et al (2002; 2003), will  allow us to measure the  objects'
position  and to determine their proper motions over a  time base of nearly
four years. The measurement  of proper motions at the  level of at least  few
tens mas/yr,   expected   for   relatively nearby  neutron   stars,   would
unambigouosly secure    the  proposed optical    identifications,  not
achievable otherwise.  In  addition, the  knowledge of  the proper  motion
will provide useful  indications  on the space velocity and distance    of
these  neutrons   stars, as   well    as  on the  radius.  Constraining these
parameters  is  of paramount importance  to discriminate  between the variety
of emission mechanisms invoked  to explain their observed thermal X-ray
spectra  and to probe the neutron star equation of state (EOS).  The
determination  of the proper  motion is a  decisive step  toward a dedicated
follow-up program aimed  at measuring  the objects' optical parallax, thus
providing     much  firmer  constrains  on  the    star properties, again to
be performed with the STIS/50CCD.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10214
Title:               ACS/HRC imaging of two very bright ultra-luminous X-ray
                     sources (ULXs)
PI:                  Roberto Soria
PI Institution:      University College London (UCL)

We propose broad- and narrow-band ACS/HRC imaging of two very bright
ultraluminous X-ray sources (ULXs) in NGC 4559. Our main objectives are: to
identify the optical counterparts; to determine their masses and evolutionary
stages; to determine the nature of mass transfer in the ULX systems; to
determine the properties of the stellar population in the ULX fields (eg,
metal abundance, age). With these observations, integrated with our Chandra,
XMM-Newton, HST/WFPC2 and CHFT data, we will test the models for the nature
and mechanisms of formation of the accreting black holes in ULXs. Moreover,
one of the two ULXs is in a peculiar star-forming complex: we have suggested
that it is an expanding wave of star-formation triggered by a dwarf galaxy
plunging through the outer disk of NGC 4559. The ACS observation will also
allow us to test this hypothesis.
================================================================================

Proposal Category:   GO
Scientific Category: AGN/QUASARS
ID:                  10215
Title:               STIS follow-up spectroscopy of Seyfert galaxies from
                     Cycle 11 near-UV imaging survey
PI:                  Thaisa Storchi-Bergmann
PI Institution:      Universidade Federal do Rio Grande do Sul

We propose a near-UV (3000-5500\AA) long-slit spectroscopic study of a sample
of 23 Seyfert galaxies with bright circumnuclear U-band structures, selected
from our Cycle 11 ACS near-UV snapshot survey. This survey collected HST U-
band images for 78 galaxies, which also have optical and near-IR images
available in the archive. We propose to enrich this image database with STIS
spectra in the near-UV. The novel aspect of the present proposal is the
availability of the near-UV images which will allow us to select the best slit
centering and orientation to probe the circumnuclear structures.    Our goal
is to investigate the nature of these structures, characterizing the
circumnuclear continuum and ionizing  source of these galaxies at a spatial
resolution of $\sim$10 parsecs, where we will probe the black hole
environment. With the proposed observations, we will derive properties of the
circumnuclear stellar populations of the selected galaxies (ages, masses and
metallicities), evolutionary effects connecting the growth of the black hole
with the growth of the galaxy bulge, as well as the relation between the black
hole mass, accretion rate (luminosity) and the circumnuclear stellar
population properties.   This dataset will also allow us to study the effect
of the bulge and black hole on the evaporation of young star clusters in these
galaxies.
================================================================================

Proposal Category:   GO
Scientific Category: COSMOLOGY
ID:                  10216
Title:               Co-evolution of spheroids and black holes
PI:                  Tommaso Treu
PI Institution:      University of California - Los Angeles

The masses of the giant black holes in galaxies are correlated with the
luminosities, masses, and velocity dispersions of their host spheroids.  This
empirical connection of phenomena on widely different scales (from sub-parsec
to kiloparsec) suggests that the evolution of a galaxy and its central black
hole are closely linked.  We propose to test various unified formation models,
by measuring the cosmic evolution of the black hole/spheroid relations, back
to z=0.37 (a lookback time of 4 Gyrs).  We will obtain 1-orbit ACS images of a
sample of 20 Seyfert 1 galaxies, for which we already have extensive new
ground-based measures of the black hole masses and the stellar velocity
dispersions.  HST resolution is required for accurate measurement of the
nonstellar AGN continuum, and the luminosity and effective radius of the bulge
of each host galaxy.  This will complete the set of observables needed to map
the co-evolution of spheroids and black-holes. The proposed sample is the
minimum required to make the first measure of the black hole mass/bulge
correlation and of the fundamental plane for active galaxies outside the local
Universe.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10217
Title:               The ACS Fornax Cluster Survey
PI:                  Andres Jordan
PI Institution:      Rutgers the State University of New Jersey

The two rich clusters nearest to the Milky Way, and the only large collections
of early-type galaxies within ~ 25 Mpc, are the Virgo and Fornax Clusters. We
propose to exploit the exceptional imaging capabilities of the ACS/WFC to
carry out the most comprehensive imaging survey to date of early-type galaxies
in Fornax: the ACS Fornax Cluster Survey. Deep ACS/WFC images -- in the F475W
(g') and F850LP (z') bands -- will be acquired for 44 E, S0, dE, dE,N and dS0
cluster members. In Cycle 11, we initiated a similar program targeting early-
type galaxies in the Virgo Cluster (the ACS Virgo Cluster Survey; GO-9401).
Our proposed survey of Fornax would yield an extraordinary dataset which would
complement that already in hand for Virgo, and allow a definitive study of the
role played by environment in the structure, formation and evolution of early-
type galaxies and their globular cluster systems, nuclei, stellar populations,
dust content, nuclear morphologies and merger histories. It would also be a
community resource for years to come and, together with the ACS Virgo Cluster
Survey, constitute one of the lasting legacies of HST.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10218
Title:               Unveiling the nature of the 321s orbital period binary
                     RXJ0806.3+1527
PI:                  GianLuca Israel
PI Institution:      INAF, Osservatorio Astronomico di Roma

This porposal is aimed at studying one of the potentially  most important
binary system in our Galaxy, namely RXJ0806.3+1527. Our group discovered a
321s periodic modulation in its optical and X-ray flux and we poposed that it
originates form the orbital motion (the shortest known) of a white dwarf
around another lighter white dwarf. VLT optical spectra showed faint and broad
(1500km/s FWHM) HeII (mainly) emission lines, even though the presence of H
can not be completely ruled out due to spectral resolution. Moreover, recent
XMM observations with the OM confirmed that the broad band energy spectrum of
this source peaks in the UV band, making it one of the best target for HST
studies. Here we propose to use the STIS spectroscopic  capability  of HST in
the TIME-TAG mode. The latter mode is extremely well suited for our purposes,
since will allow us, among other things, to perform, for the first time, an
Orbital Phase Spectroscopy  of the expected He lines (also those of C, N and O
are expected) in the STIS spectra. We expect to finally probe the nature of
the source by following the emission line centroid shift as a function of the
orbital phase, making RXJ0806.3+1527 a single-component spectroscopic binary
and opening  a new perspective in the field of double degenerate systems (the
emission lines of the greatest part of which are dominated by the effect of
the disk rotation).
================================================================================

Proposal Category:   GO
Scientific Category: STAR FORMATION
ID:                  10219
Title:               Are Dust Disks and Circumstellar Gas Around Young A Stars
                     Unrelated Phenomena?
PI:                  James Neff
PI Institution:      College of Charleston

Young stars with circumstellar material are common, but their properties vary
greatly. Current studies strongly suggest that Beta Pictoris (A5 V) is an
early solar system. If the high-density, high-velocity circumstellar gas
falling toward Beta Pic were fueled by grazing comets or on-going erosion of
debris located close to the star, we would expect to find evidence for warm
dust in all Beta Pic-like systems. We have carried out detailed studies of the
circumstellar environments of all nearby A-type stars.  We have studied not
only their circumstellar dust but also the characteristics of their
circumstellar gas through absorption line spectroscopy. Based on our visible
and IUE data, we identified about a dozen A-type stars with circumstellar gas.
Among them, 7 have dynamic circumstellar gas similar to that found in the Beta
Pic system, but none of them has detectable IRAS infrared excess. What is the
origin of the dynamic circumstellar gas around young A-type stars? The STIS
wavelength range covers many fine-structure lines that can only be seen at
high densities, which are characteristic of circumstellar but not interstellar
gas. We propose to observe these 7 stars with STIS to (a) verify the
circumstellar gas detections from our previous visible and IUE studies, (b)
determine the temperature and electron number density in the circumstellar
gas, (c) derive accurate circumstellar gas column densities, and (d) study the
possible causes of the variable circumstellar absorption lines (both red-
shifted and blue-shifted have been seen in spectra of Beta Pic and our 7
target stars).
================================================================================

Proposal Category:   GO
Scientific Category: COOL STARS
ID:                  10220
Title:               Probing the Nucleosynthesis Products of the First Stars
PI:                  Christopher Sneden
PI Institution:      University of Texas at Austin

We propose the first extensive HST study of Galactic halo stars that are
deficient in heavy (i.e., neutron-capture) elements. These so-called r-
process-poor stars contain the nucleosynthesis products from the earliest
generations of  stars, the progenitors of the halo stars. Detections of the
lightest neutron-capture elements, such as Ge, along with some of the
heaviest, including Pt, can only be obtained in the NUV. Our HST abundance
analysis of the well-known bright (r-process-poor) giant star HD 122563
indicates a surprising drop off in neutron-capture element abundances from Ge
to Pt. This is in contrast to the solar pattern seen in r-process-rich stars,
and suggests that some of the very earliest generations of stars were unable
to synthesize the heaviest elements. To confirm and strengthen this finding we
will obtain abundance determinations for a number of neutron-capture elements
in a target sample of 8 stars, spanning a wide range of metallicity. The
resulting abundance distributions will provide a direct indication of the
nucleosynthetic conditions (such as temperatures, densities, and neutron
fluxes) in the halo progenitors. These in turn will help to identify the
characteristics (such as masses and metallicities) and nature of the first
stars in the Galaxy.
================================================================================

Proposal Category:   GO
Scientific Category: STAR FORMATION
ID:                  10221
Title:               Uncovering the unknown Ly-alpha flux in classical T Tauri
                     stars
PI:                  Gregory Herczeg
PI Institution:      University of Colorado at Boulder

The FUV emission of CTTSs significantly impacts the chemical evolution and
aids in the dispersal of gas in protoplanetary disks.  Despite its importance,
the dominant source of FUV emission, H I Ly-alpha at 1215.67 A, is not
directly observable due to neutral hydrogen absorption in our line of sight to
nearly all young stars.  We have recently developed a novel technique to
indirectly measure the Ly-alpha emission incident on the disk using Ly-alpha
pumped molecular hydrogen emission lines, which are detected throughout the UV
spectra of CTTSs.  Measuring the Ly-alpha flux has a large effect of the total
FUV emission from CTTSs:  results from test cases demonstrate that at least
75% of the FUV emission is in this one line.  The lack of accurate
measurements of Ly-alpha remains a glaring weakness in chemical models of
protoplanetary disks and disk dispersal.  This strong emission will create a
Ly-alpha dominated PDR-like disk surface at planet-forming radii close to the
star.  We propose using molecular hydrogen emission to reconstruct the
intrinsic Ly-alpha line from three CTTSs to understand the dominant FUV
emission source from these stars and its effect on protoplanetary disks.
================================================================================

Proposal Category:   SNAP
Scientific Category: GALAXIES
ID:                  10222
Title:               The Next Generation Spectral Library
PI:                  David Silva
PI Institution:      European Southern Observatory - Germany

We propose to complete our snapshot program to produce a Next Generation
Spectral Library of 600 stars for use in modeling the integrated light of
galaxies and clusters.  This program is using the low dispersion UV and
optical gratings of STIS.  The library will be roughly equally divided among
four metallicities, very low ([Fe/H] < -1.5), low (-1.5 < [Fe/H] < -0.5),
near-solar (-0.3 < [Fe/H] < 0.1), and super-solar ([Fe/H] > 0.2), well-
sampling the entire HR-diagram in each bin.  Such a library will surpass all
extant compilations and have lasting archival value, well into the Next
Generation Space Telescope era.  Because of the universal utility and
community-broad nature of this venture, we waive the entire proprietary
period.
================================================================================

Proposal Category:   GO
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID:                  10223
Title:               Probing a damped Lyman-alpha system along two lines of
                     sight
PI:                  Nicholas Morgan
PI Institution:      Yale University

Damped Lyman-alpha absorption systems hold key information about galaxy
formation and chemical evolution of the Universe. We have recently discovered
that the bright (V = 15.4) z=1.07 quasar HS 2209+1914 is a gravitationally
lensed double with an image separation of 1.1 arcsec and a clearly detected
lensing galaxy.  A strong Mg II and Fe II absorption system at z=0.51 is very
suggestive of a common damped Ly-alpha absorber (DLA) in both lines of sight,
presumably identical with the lensing galaxy.  We propose to obtain UV
spectroscopy of both QSO components, with the principal aim to confirm the DLA
hypothesis and obtain the column density of neutral hydrogen along both lines
of sight.  This will enable future high-resolution spectroscopy to determine
elemental abundances and their spatial variance between different locations in
the absorber. In combination with new ground-based deep infrared images, HS
2209+1914 will be the only known DLA galaxy where spatially resolved abundance
information can be directly related to the observed distribution of stellar
light. Byproducts of our study will include new insights into the lensing
geometry of the system, a high S/N measurement of differential extinction
through the lensing galaxy, and an estimate of the lensing galaxy's extinction
curve.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10224
Title:               Spatially Resolved mid-UV Spectra of the Centers of Local
                     Group Galaxies
PI:                  Ricardo Schiavon
PI Institution:      The University of Virginia

We propose to use STIS to collect medium resolution mid-UV and optical spectra
from the nuclei of M31, M32 and NGC 205. The observations will  provide
fundamental constraints to the stellar population models we are currently
developing in our Treasury Program (GO-9455, PI Ruth Peterson). The data will
also be useful to constrain the stellar population content in the centers of
the target galaxies. Last but not least, they will be crucial templates for
studies of distant galaxies, by providing a direct assessment of
spectrophotometric evolution in the mid-UV.
================================================================================

Proposal Category:   GO
Scientific Category: AGN/QUASARS
ID:                  10225
Title:               Abundances in AGN outflows: Putting Real Numbers Into
                     Quasar Feedback Scenarios
PI:                  Nahum Arav
PI Institution:      University of Colorado at Boulder

AGN outflows impact the evolution of supermassive black holes, host galaxies,
and the surrounding IGM. To assess the importance of these processes, it is
essential to obtain the physical properties of real AGN winds. Our proposed
HST/STIS observations of the Seyfert 1 galaxy Mrk 509, in combination with
dedicated FUSE time, are designed to obtain the first reliable determination
of chemical abundances for an AGN outflow. Previous attempts to measure
abundances from outflow absorption troughs did not account for velocity
dependent covering factors of the absorbers. This led to large uncertainties
in measuring absorption column densities, uncertainties which are magnified
when translated to abundances. To extract reliable column densities, we
created an array of analysis tools for modeling high-S/N echelle data of
doublets and higher multiplet lines from the same ion.  After carefully
reviewing all the available targets we conclude that the combination of high
UV flux and unblended outflow troughs makes Mrk 509 the most promising target
for obtaining abundances in AGN outflows. Our proposed Mrk 509 observations
will provide the best input to date for accurately modeling the influence of
AGN winds on the galactic and inter-galactic environments.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10226
Title:               The NICMOS Grism Parallel Survey
PI:                  Matthew Malkan
PI Institution:      University of California - Los Angeles

We propose to continue our NICMOS pure parallel imaging and spectroscopic
program.  Our team has now built up considerable experience in optimizing the
scheduling,  reduction and analysis of NICMOS parallel observations. For a
modest investment, our enhanced emphasis on G141 grism spectroscopy will
increase the number of line-emitting  galaxies detected by a factor of ~ 5-10.
As our previous work demonstrated, the most frequently  detected line is
Halpha at 0.770 AU); at such large distances around GJ
803, dust evolutionary timescales are longer than the stellar age, and hence
we can study the composition of primordial circumstellar material.  The
combined dataset will provide the most comprehensive study to date of a debris
disk from  ~7 AU to ~200 AU radius.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10229
Title:               Space Motions for the Draco and Sextans Dwarf Spheroidal
                     Galaxies
PI:                  Slawomir Piatek
PI Institution:      New Jersey Institute of Technology

We will use the powerful astrometric capabilities of HST to measure proper
motions for the Draco and Sextans dwarf spheroidal galaxies that will yield
tangential velocities accurate to about 30 km/s.  These two galaxies are the
last inside a galactocentric radius of 200~kpc without measured proper
motions.  Knowing their orbits is critical for our understanding of the low-
luminosity satellites of the Milky Way.  In particular they are critical for
understanding why Ursa Minor has survived tidal disruption on its plunging
orbit and how Carina formed a large intermediate-age stellar population
despite its small mass.
================================================================================

Proposal Category:   GO
Scientific Category: AGN/QUASARS
ID:                  10230
Title:               Radial Velocity Variability in the Mass Outflow in the
                     Seyfert 1 Galaxy NGC 3783
PI:                  Jack Gabel
PI Institution:      University of Colorado at Boulder

We have discovered a decreasing radial velocity in an outflowing UV absorber
in NGC 3783 -- the first unambiguous detection of kinematic variability in an
AGN outflow.  The observed velocity shift could be due either to bulk
deceleration of the outflow or a geometric effect, in which the radially
projected component of velocity changes as the outflow moves across our line
of sight. Several pieces of evidence support the latter interpretation.  A
simple geometric model of an absorber with a changing velocity vector predicts
the absorption line depths will decrease sometime before mid-2005, at an
increasingly rapid rate, and eventually disapper.  We propose three STIS E140M
observations, obtained at 4 -- 8 months intervals, to determine the underlying
mechanism causing this rare phenomenon.  Specifically, these observations will
allow us to: 1) track the radial velocity variations, 2) follow the evolution
of the covering factors, thereby mapping the geometry and transverse motion of
the absorber against the background AGN light, 3) determine the ionization
structure in the outflow by monitoring ionization-dependent coverage, and 4)
test for changes in the ionization of the absorber using photoionization
models.  These results will provide a definitive test of the geometric model,
and will place strong limits on alternative mechanisms.   In addition, we have
also been allocated two FUSE observations of NGC 3783 in the upcoming cycle.
We request simultaneous observations in at least one epoch, which will place
very tight constraints on the absorption/emission geometry.  These results
will provide crucial input needed to test dynamical models  of AGN outflows.
================================================================================

Proposal Category:   GO
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID:                  10231
Title:               Tracing the Reionization History of Intergalactic Helium
                     out to Redshift 3.8
PI:                  Wei Zheng
PI Institution:      The Johns Hopkins University

We have found He II absorption in a quasar at redshift 3.82 via our Cycle 12
program of UV snapshots. This is the highest redshift yet at which He II
absorption has been observed, and we propose a high S/N STIS follow-on
spectrum to study helium ionization in the IGM along this new, long,
unobscured sightline to high-redshift. The object has UV flux comparable to
that of the rare handful of other z>3 quasars known to be suitable for helium
studies, and it is also in the Continuous Viewing Zone, permitting a high-
quality STIS spectrum in just 8 HST orbits. The proposed spectrum will allow
us to study the evolution and properties of the IGM and ionizing radiation
from z=3.8 (the IGM environment near the quasar) all the way down to z=2.8.
This redshift range may span the epoch of helium reionization, and even
extends to high enough redshift to enable improved helium opacity measures
using both He II Ly-alpha and Ly-beta.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10232
Title:               Constraining Models of Galactic Chemical Evolution and
                     Mixing by Measuring the Spatial Variability of D/H in the
                     Interstellar Medium
PI:                  Scott Friedman
PI Institution:      Space Telescope Science Institute

Measuring the abundance of deuterium relative to hydrogen in the interstellar
medium provides a method to assess the effects on the D/H ratio of astration
and subsequent chemical enrichment of the ISM by supernovae, massive star
winds, infalling gas, and mixing.  It is now well established that D/H is
approximately constant within the Local Bubble, at distances <~ 100 pc.  At
greater distances there is limited but growing evidence that it varies.
However, confirmation of this, and a more definitive interpretation of the
variability, requires improved measurements of the HI column density, which
can only come from STIS measurements of the Ly alpha line.  We request
observations of 7 targets, all well outside the Local Bubble based on their DI
column densities, to establish the degree of variability with high confidence.
FUSE observations to determine N(DI) are complete for 5 targets, the remaining
~30% of the data on a 6th target is scheduled to be obtained at the end of
January, 2004, and the last target is part of an accepted FUSE cycle 5
program.  With the improved HI column densities obtained with the observations
proposed here, we will confirm the variability indicated by a small number of
IMAPS and FUSE sight lines, and we will place important constraints on models
of chemical evolution and mixing.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10233
Title:               Determining the Instability Strip for Accreting White
                     Dwarfs
PI:                  Paula Szkody
PI Institution:      University of Washington

Using UV observations with STIS in Time-Tag mode, we will obtain spectra of 3
newly discovered pulsating white dwarfs found among recent  cataclysmic
variables identified in the SDSS.  Our Cycle 8 observations of the only
previously known accreting, pulsating, white dwarf in GW Lib revealed large
amplitude UV pulsations, a spectrum that showed metals and required a dual
temperature fit with a high white dwarf mass. Since accretion likely causes
abundance, rotation, and atmospheric  temperature differences in accreting
white dwarfs versus single  white dwarfs, we will use these  systems to
explore the location of the instability strip for accreting white dwarfs and
determine whether they are all massive and spotted objects. Light curves can
be constructed at different wavelengths to aid in mode identification. Having
knowledge of the atmospheres and interior structure of 4 sytems will provide
great insight into the interaction of accretion, stellar pulsation and long
term evolution. Due to optical contamination by the disk, stream, and/or
secondary, the UV is the optimum regime to study pulsating, accreting white
dwarfs.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10234
Title:               A search for gamma Cas analogs at low metallicity
PI:                  Luciana Bianchi
PI Institution:      The Johns Hopkins University

Extensive studies of Be stars in the Milky Way (MW), from optical to X-Ray
wavelengths, showed that this class of objects gives important clues to our
understanding  of issues of broad relevance, among them the dynamo mechanism,
stellar evolution (single/binary),  circumstellar disks, variability and
mechanisms for X-ray emission. Moreover, the classical prototype (from optical
studies) of this class, gamma Cas, has turned out to be unique in its X-ray
properties.  Can we find gamma Cas analogs in other galaxies? How does the Be
phenomenon depend on metallicity ?       We propose to extend the study of Be
stars to the low metallicity Small Magellanic Cloud (SMC). We selected a
small, exploratory but significant, sample of Be stars detected from our
extensive ground-based surveys.  Because many crucial properties can only be
measured in the  UV, we propose to obtain  STIS UV spectra to complement our
data at other wavelengths  (ground-based, including light curves and Halpha,
and X-rays) , in order to: (1) characterize the SMC counterpart of the Be
class, so far only (and extensively) studied in the UltraViolet in the MW, in
the parameter space Teff, Lbol, mass loss, and (2) perhaps detect  analogs of
the hitherto unique object  gamma Cas.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10235
Title:               Dark vs. luminous matter in the CenA/M83 galaxy complex
PI:                  Igor Karachentsev
PI Institution:      Russian Academy of Sciences, Special Astrophysical Obs.

The distribution of dark vs. luminous matter on scales of 0.1-1.0 Mpc remains
poorly understood. For a nearby group, the total mass can be determined from
the radius of "the zero-velocity surface", which separates the group from the
general Hubble flow. This new method requires the measurement of accurate
distances and radial velocities of galaxies around the group, but gives total
mass estimates independent of assumptions about the state of relaxation or
orbital characteristics. The mass pertains to the group at the full scale to
which it is bound. Upon application in several nearest groups, the method
yields mass estimates in agreement with the sum of the virial masses of
subcomponents. However, the typical total M/L ratio for the nearby groups of
~30 Mo/Lo implies a local mean density of matter which is only 1/7 the
canonical global density . The nearby complex of galaxies around Cen A and M83
resembles our Local Group by the dumb-bell concentration of objects around a
pair of dominant galaxies. Accurate distances have been acquired recently for
~20 group members by the TRGB method using HST. We will measure TRGB distances
to the 17 remaining galaxies in the region. These observations will constrain
the dynamical state of the halo surrounding the nearest giant E-galaxy Cen A,
providing a comparison with the halos of the nearest spirals.
================================================================================

Proposal Category:   SNAP
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10236
Title:               A SNAPSHOT Survey of the Local Interstellar Medium: New
                     NUV Observations of Stars with Archived FUV Observations
PI:                  Seth Redfield
PI Institution:      University of Texas at Austin

We propose to obtain high-resolution STIS E230H SNAP observations of MgII and
FeII interstellar absorption lines toward stars within 100 parsecs that
already have moderate or high-resolution far-UV (FUV), 900-1700 A,
observations available in the MAST Archive.  Fundamental properties, such as
temperature, turbulence, ionization, abundances, and depletions of gas in the
local interstellar medium (LISM) can be measured by coupling such
observations.  Due to the wide spectral range of STIS, observations to study
nearby stars also contain important data about the LISM embedded within their
spectra.  However, unlocking this information from the intrinsically broad and
often saturated FUV absorption lines of low-mass ions, (DI, CII, NI, OI),
requires first understanding the kinematic structure of the gas along the line
of sight.  This can be achieved with high resolution spectra of high-mass
ions, (FeII, MgII), which have narrow absorption lines, and can resolve each
individual velocity component (interstellar cloud).  By obtaining short (~10
minute) E230H observations of FeII and MgII, for stars that already have
moderate or high-resolution FUV spectra, we can increase the sample of LISM
measurements, and thereby expand our knowledge of the physical properties of
the gas in our galactic neighborhood.  STIS is the only instrument capable of
obtaining the required high resolution data now or in the foreseeable future.
================================================================================

Proposal Category:   GO
Scientific Category: AGN/QUASARS
ID:                  10237
Title:               Low-Ionization BALs: Evolution or Orientation?
PI:                  Xiaohui Fan
PI Institution:      University of Arizona

We propose to test the hypothesis that Low-Ionization Broad Absorption Line
Quasars (LoBALs) represent a special stage of quasar evolution: young quasars
in systems with strong interaction and star-formation.  We will carry out high
resolution imaging using ACS/WFC and NICMOS to measure the properties of the
host galaxies of four LoBAL quasars at z = 0.9 - 2.0 that show strong
overlapping FeII absorption troughs. The ACS imaging will be carried out in
the passband with the strongest BAL absorption, acting as a natural
coronagraph. This results in a reduction of quasar light by a factor of 15 -
26 in these passbands, providing arguably the best view of the host galaxies
of luminous, high-redshift quasars. This method allows efficient detection and
detailed modeling of the host galaxy morphology in the rest-frame ultraviolet,
which is most sensitive to star formation and galaxy interaction.  We will
also use NICMOS imaging to measure the rest-frame light from the host galaxy
to probe the old stellar populations where the host galaxy is likely to be
brighter. It has been suggested that LoBALs might not be explained simply as
an orientation effect but rather as an early phase of quasar evolution.  Such
a phase is typically associated with large amounts of dust and gas, and young
galaxies with strong star formation.  With HST observations, we will study the
color and morphology of the FeLoBAL quasar host galaxies, and measure the age
of their dominant stellar populations.  We will also measure the density of
close companions, and, in particular, look for signs of ongoing or recent
mergers.  These measurements will be compared to those of control samples of
normal quasars at similar redshift.  If LoBALs are indeed young systems, then
their host galaxies are expected to show stronger interactions and merger
activity, younger stellar ages, and regions with strong star formation.  If
the LoBAL host galaxies show no significant difference from those of normal
quasars, it will support the view that LoBAL quasars are not a distinct
population and that all quasars have BAL outflows along some lines of sight.
================================================================================

Proposal Category:   GO
Scientific Category: AGN/QUASARS
ID:                  10238
Title:               The nature of  quasar host galaxies: combining ACS
                     imaging and VLT Integral Field Spectroscopy.
PI:                  Frederic Courbin
PI Institution:      Universite de Liege

We  propose to  perform ACS/F606W  imaging of  a complete sample of  29
quasar host galaxies (0.08~ 10% solar) extending up
to 50 or even 100 kpc. The 19 CVZ orbits requested will also allow us to
determine some simple kinematics for this halo gas.  The edge-on Sc galaxy ESO
157-G049 and the triple system of bright QSOs that all probe its halo within a
projected distance of 125 kpc is unique - we have searched the entire sky for
bright QSOs within 150 kpc of nearby galaxies and no other nearby galaxies are
probed by three QSOs bright enough to be observed with HST/STIS. Our Cycle 11
snapshot program has measured accurate far-UV fluxes for these QSOs and has
already made probable detections of Ly-alpha absorption associated with this
galaxy in 2 of the QSO sight lines.
================================================================================

Proposal Category:   SNAP
Scientific Category: STELLAR POPULATIONS
ID:                  10255
Title:               A Never Before Explored Phase Space:  Resolving Close
                     White Dwarf / Red Dwarf Binaries
PI:                  Donald Hoard
PI Institution:      California Institute of Technology

We propose an ACS Snapshot imaging survey to resolve a well-defined sample of
highly probable white dwarf plus red dwarf close binaries.  These candidates
were selected from a search for white dwarfs with infrared excess from the
2MASS database.  They represent unresolved systems (separations less than
approximately 2" in the 2MASS images) and are distributed over the whole sky.
Our HST+ACS observations will be sensitive to a separation range (1-20 AU)
never before probed by any means.  The proposed study will be the first
empirical test of binary star parameters in the post-AGB phase, and cannot be
accomplished from the ground.  By resolving as few as 20 of our 100 targets
with HST, we will be able to characterize the distribution of orbital semi-
major axes and secondary star masses.
================================================================================

Proposal Category:   GO
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID:                  10256
Title:               Doubling the Data on the HeII Re-ionization of the
                     Intergalactic Medium
PI:                  David Tytler
PI Institution:      University of California - San Diego

We propose to double the existing information on the ionization of HeII in the
IGM at redshifts around 3.  We will observe 3 QSOs that are bright in the far
UV.  Each will give a moderate resolution HST spectrum better than any
obtained so far.  We will also observe a fourth QSO that currently lacks high
SNR spectra.  This program addresses a central issue in cosmology: the
reionization of the intergalactic medium (IGM).  Current theoretical models
predict that H I  starts to reionize around z=17, completing near 6, while
HeII reionization is delayed until z=3. The theoretical models of the
ionization of  HeII in the IGM now offer more detailed predictions that the
data can distinguish. The new spectra will provide the data required to
distinguish between different  reionization scenarios, by increasing the
number of lines of sight near z=3 with good spectra from 3 to 7, 3 of which
will have the best sensitivity to the HeII optical depth. For the first time
we also explore the 3-dimensional distribution of the ionizing regions, to
characterize the luminosity and number density of the ionizing sources.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10257
Title:               Astrometric and Photometric Study of NGC 6397 for
                     Internal Motions, Dark Binaries, and X-Ray Sources
PI:                  Jay Anderson
PI Institution:      Rice University

We propose to observe the central regions of the globular cluster NGC 6397
with ACS/WFC once per month for the 10 months of its visibility in Cycle 13.
The project has three main goals:  (1) Measure internal motions for roughly
3000 stars within 150 arcseconds of the cluster center, using archival WFPC2
as a first epoch.  The motion of the typical star will be measured to 10-20%.
We will detect any central black hole (BH) with a mass greater than 1000 solar
masses, and will also measure core-collapse signatures such as anisotropy.
(2) Conduct the first-ever search for heavy binaries by looking for the
astrometric "wobble" of the luminous secondary.  We should find all heavy
binaries in the field with separations between 1 and 5 AU and periods between
3 months and 5 years. (3) Search for opticall counterparts to X-ray sources
found by Chandra.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10258
Title:               Tracing the Emergence of the Hubble Sequence Among the
                     Most Luminous and Massive Galaxies
PI:                  Claudia Kretchmer
PI Institution:      The Johns Hopkins University

There is mounting evidence that the redshift range 1 < z < 2 was an important
era when massive galaxies assembled their stellar content and assumed their
present--day morphologies.  Despite extensive HST imaging surveys, however,
there is very little data in the optical rest frame (i.e., observed near--
infrared) on the morphologies of the most luminous galaxies at these
redshifts. We propose to image a carefully selected set of 20 of the most
luminous, K--band selected GOODS galaxies at 1.3 < z < 2, using NICMOS camera
2.  This offers diffraction--limited, critically sampled imaging at 1.6
microns to ensure the best angular resolution for comparison to ACS.  The
galaxies are chosen to span a simple 4--fold parameter space of morphological
and spectral type, in order to provide the most information about the
varietyof massive galaxy properties in this redshift range.  We will
investigate the emergence of large scale--length disks, stable spiral
structure, mature bulges with red stellar populations, central bar structures,
the incidence of disturbed morphology, the existence (or lack thereof) of blue
ellipticals, and other questions that concern the evolution and maturation of
the brightest, largest, and most massive ordinary galaxies in this critical
redshift range.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10259
Title:               Planetary nebulae in the SMC: a study of stellar
                     evolution and populations in an extremely low-metallicity
                     environment
PI:                  Letizia Stanghellini
PI Institution:      Space Telescope Science Institute

The final phase of the evolution of low- and intermediate-mass stars, the
planetary nebula (PN) ejection, is thought to largely contribute to the carbon
and nitrogen enrichment in galaxies, in particular in old stellar populations.
Stellar generations forming from a carbon- and nitrogen-enriched medium are a
necessary condition for planetary and life formation. It is essential to
understand how stars go through the process of shedding their chemically-
enriched shells, and to test the predictions of stellar evolution theory on
the  relationship between stellar mass and elemental enrichment.  Magellanic
Cloud  PNs are ideal probes for this study. Their abundances can be directly
related to the mass of the central stars and to that of the stellar
progenitor, without the great (distance and reddening) uncertainties that
affect Galactic PNs.  The UV lines are essential for calculating the
abundances of the element related to stellar evolution (C, N, O) and to
progenitor populations (e.g., Ne). We propose to acquire STIS UV spectroscopy
of the SMC PNs whose morphology and central star properties has been
previously determined by us with HST. We will derive the (C, N, O) abundance-
to-mass relation, and determine the extent to which the mass of the
progenitors of asymmetric PNs exceed that of symmetric PNs. We will also test
the PN luminosity function, and probe cosmic recycling, in a very low-
metallicity environment.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10260
Title:               The Most Massive Star Clusters:  Supermassive Globular
                     Clusters or Dwarf Galaxy Nuclei?
PI:                  William Harris
PI Institution:      McMaster University

Evidence is mounting that the most massive globular clusters, such as Omega
Centauri and M31-G1, may be related to the recently discovered "Ultra-Compact
Dwarfs" and the dense nuclei of dE,N galaxies.      However, no systematic
imaging investigation of these supermassive globular clusters -- at the level
of Omega Cen and beyond -- has been done, and we do not know what fraction of
them might bear the signatures (such as large effective radii or tidal tails)
of having originated as dE nuclei.  We propose to use the ACS/WFC to obtain
deep images of 18 such clusters in NGC 5128 and M31, the two nearest rich
globular cluster systems.  These globulars are the richest star clusters that
can be found in nature, the biggest of them reaching 10^7 Solar masses, and
they are likely to represent the results of star formation under the densest
and most extreme conditions known.   Using the profiles of the clusters
including their faint outer envelopes, we will carry out state-of-the-art
dynamical modelling of their structures, and look for any clear evidence
which would indicate that they are associated with stripped satellites.  This
study will build on our previous work with STIS and WFPC2 imaging designed to
study the 'Fundamental Plane' of globular clusters. When our new work is
combined with Archival WFPC2, STIS, and ACS material, we will also be able to
construct the definitive mapping of the Fundamental Plane of globular clusters
at its uppermost mass range, and confirm whether or not the UCD and dE,N
objects occupy a different structural parameter space.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10261
Title:               The Formation Mechanisms of Extreme Horizontal Branch
                     Stars
PI:                  Thomas Brown
PI Institution:      Space Telescope Science Institute

We propose far-UV spectroscopy of NGC 2808, in order to better understand the
formation mechanisms for extreme horizontal branch (EHB) stars.  Our recent
analysis of STIS UV imaging has revealed an unusual population of subluminous
EHB stars in this cluster, an anomaly that is unexplained by canonical stellar
evolution theory. Using new theoretical models of evolution, atmospheres, and
spectra, we have demonstrated that these subluminous stars could be the
product of a late helium core flash, which occurs while the stars are on the
white dwarf cooling curve. The convection zone produced by such a flash will
penetrate the hydrogen envelope, mixing hydrogen into the hot helium-burning
interior, where it is rapidly consumed.  The resulting EHB star would exhibit
greatly enhanced helium and carbon at its surface, and would appear
subluminous in the UV.  Furthermore, the dichotomy between the normal EHB
stars and the hotter flash-mixed EHB stars would explain the hottest gap
observed in the HB distribution of NGC 2808.  Far-UV spectroscopy of normal
and subluminous EHB stars in this cluster will unambiguously test this new
formation mechanism.  The results will also advance our understanding of
abundance anomalies in subdwarf B and O stars, the UV emission from elliptical
galaxies, and the "born again" scenario for producing hydrogen-deficient R CrB
stars.
================================================================================

Proposal Category:   GO
Scientific Category: COOL STARS
ID:                  10262
Title:               The 3D Morphology of the Extreme Red Supergiant VY CMa
PI:                  Roberta Humphreys
PI Institution:      University of Minnesota - Twin Cities

The extreme RSG and powerful OH/IR source VY CMa is surrounded by an
asymmetric reflection nebula dominated by a prominent nebulous arc, bright
filamentary arcs, and several clumps of dusty knots that are evidence for
multiple and asymmetric mass loss events. Our groundbased velocities show that
these structures are kinematically distinct from the gneral flow of the
diffuse gas and may be directional. We have speculated that these arcs and
knots may be caused by localized activity on the star involving convection and
possibly magnetic fields analogous to lower mass stars. If correct this would
have important implications for the causes of high mass loss events in evolved
massive stars. Fortunately, VY CMa provides us with an opportunity to learn
more about its possible mass loss mechanisms and history from the morphology
of its ejecta. We propose to use polarimetry and second epoch images combined
with our radial velocities to map the morphology of the nebula and the
discrete structures embedded in it.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10263
Title:               SAINTS - Supernova 1987A INTensive Survey
PI:                  Robert Kirshner
PI Institution:      Harvard University

SAINTS is a program to observe SN 1987A, the brightest supernova in 383
years, as it transforms into supernova remnant (SNR) 1987A, the youngest
supernova remnant. HST is the unique and perfect match in scale and in field
for spatially-resolved observations of SN 1987A. Rapid changes are taking
place in a violent encounter between the fastest-moving debris and the
circumstellar ring.  This one-time-only event, leading to suddenly appearing
hotspots and new emission that can reveal previously hidden gas, is powered by
shocks that can be studied simultaneously with HST and with Chandra to great
advantage.  Both the optical and X-ray flux from the ring are rising rapidly
so prompt observations are needed in Cycle 13.  Our previous observations
reveal a remarkable reverse shock  moving  upstream through the expanding
debris. The reverse shock provides a powerful tool for dissecting the radial
structure of the vanished star. The debris from the explosion itself, still
excited by radioactivity, is now well resolved by ACS and seen to be
aspherical, providing direct clues to the mechanism of the explosion. Many
questions about SN 1987A remain unanswered.  SAINTS is a comprehensive attempt
to use HST to establish the facts of SN 1987A, help to answer interesting
questions, and to observe the birth of SNR 1987A.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10264
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 is
small, other SN may occur within 100 kpc and in most scenarios the optical
counterpart will be much brighter than traditionally studied extragalactic SNe
and therefore of great scientific interest.  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 images will have major
public outreach value and will be released immediately by NASA.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10265
Title:               The Formation History of Andromeda
PI:                  Thomas Brown
PI Institution:      Space Telescope Science Institute

We propose deep observations of Andromeda's outer disk and giant tidal stream,
to reconstruct their star formation histories.  As the nearest giant galaxy,
Andromeda offers the best testing ground for understanding galaxy formation
and evolution.  Given the dramatic increase in sensitivity offered by the ACS,
we can now resolve stars on the old main sequence in the other giant spiral of
the Local Group, and employ the same direct age diagnostics that have been
used for decades in the study of Galactic globular clusters.  In Cycle 11, we
successfully observed a field in the Andromeda halo and constructed a deep
color-magnitude diagram reaching well below the oldest main sequence turnoff.
In Cycle 13, we propose to extend these observations to the outer disk and
tidal stream of Andromeda, to constrain their star formation histories and
compare them to that of the halo. The combined observations from these two
programs will offer a dramatic advance in our understanding of the overall
evolution of spiral galaxies.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10266
Title:               Origins of the Highly Ionized Gas toward the X-ray Bright
                     BL Lac Object Mrk 421
PI:                  Blair Savage
PI Institution:      University of Wisconsin - Madison

The X-ray bright BL Lac object Mrk 421 is one of the small number of
extragalactic objects for which it is possible to study the highly ionized gas
in the ISM and Local Group using the full diagnostic power of UV, far-UV and
X-ray observatories. High quality far-UV observations of OVI and other ions
have been obtained by FUSE, whereas Chandra and XMM-Newton have provided X-ray
measurements of extremely strong OVII and OVIII absorption at redshift zero.
It has been proposed that the OVI, OVII, and OVIII originate together in the
warm-hot intergalactic medium, of the kind predicted by numerical simulations
to contain a substantial fraction of the baryons at z=0. However, the
properties of the high-ion absorption are also consistent with an origin in an
extended Galactic Corona. Data for other species such as SiIII, SiIV, and CIV
will be essential to determine whether or not a Local Group WHIM filament has
been detected. These species are not expected to be seen in a hot (T > 10^6 K)
medium and their detection at the same velocity as OVI would suggest that the
OVI samples a different phase of the gas than the OVII and OVIII. We propose
to obtain a high quality 7 km/s resolution STIS UV spectrum of Mrk 421 from
1150 to 1700 A. The STIS measurements of CII, CIV, SiIII, SiIV, and other
species will allow us to evaluate the ionization conditions in the absorbing
gas in the Galactic thick disk and in an anomalous high positive velocity
absorption wing currently only traced by OVI and CIII. The ionic ratios among
these species will provide critical tests of the ionization mechanisms
affecting the OVI absorption.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10267
Title:               The Shadow Echoes of the Unique R Coronae Borealis Star,
                     UW Cen
PI:                  Geoffrey Clayton
PI Institution:      Louisiana State University & Agricultural & Mechanical
                     Colle

Understanding the R Coronae Borealis (RCB) stars is a key test for any theory
aiming to explain hydrogen deficiency in post-AGB stars. The RCB stars are
rare hydrogen-deficient carbon-rich supergiants that undergo very spectacular
declines in brightness of up to 8 magnitudes at irregular intervals as dust
forms near the star along the line of sight. UW Cen is unique among the cool
RCB stars in having a visible circumstellar shell. The morphology of the
nebula appears to change as different parts are illuminated by light from the
central star modulated by shifting, thick dust clouds near its surface. The
central star acts like a "lighthouse," shining through gaps between the near-
star dust clouds, and lighting up different portions of the outer nebula. We
propose a scientific program in which a small number of observations using
ACS/HRC will exploit UW Cen's unique circumstellar shell to address two
critical elements in understanding RCB stars: determining an accurate distance
to the star, and studying the otherwise unobservable dust clouds forming near
the star's surface.  We will model the images using Monte Carlo techniques to
calculate the radiative transfer through arbitrary distributions of dust
viewed from any angle.
================================================================================

Proposal Category:   GO
Scientific Category: SOLAR SYSTEM
ID:                  10268
Title:               Recovery of three faint Kuiper Belt Objects discovered
                     with HST
PI:                  David Trilling
PI Institution:      University of Pennsylvania

We propose 6 orbits to make ACS/WFC follow-up observations of three faint
Kuiper Belt Objects (KBOs) that we discovered in the Large Cycle 11 program GO
9433 (G. Bernstein, PI; Bernstein et al. 2004). These KBOs are the faintest --
and therefore smallest -- KBOs known. Two of these objects can be recovered
(and the third easily recovered and its colors probed) only with HST. Any
future studies of small KBOs will require knowledge of our three faint KBOs.
With the proposed observations, the locations of these KBOs will be known
quite well until after first light for JWST. Without the proposed
observations, these three small KBOs will be effectively lost. This small
program represents a small investment of HST time to solidify the legacy of
the Bernstein et al. Large GO program.  With the proposed observations, we
will be able to determine with certainty the dynamical classes of these three
KBOs, testing the hypothesis that small KBOs are predominantly classical KBOs.
We will also test the suggestion that classical KBOs are uniformly quite red.
Lastly, our observations will enable physical studies (e.g., spectroscopy)
with JWST a decade from now. All these measurements will provide important
evidence for theories on the formation and evolution of the Solar System.
================================================================================

Proposal Category:   GO
Scientific Category: SOLAR SYSTEM
ID:                  10269
Title:               The Relative Roles of  Volcanism and Sublimation in
                     Supporting Io's Atmosphere
PI:                  John Spencer
PI Institution:      Southwest Research Institute

We propose disk-resolved 2000-3150 A spectroscopy of Io's unique SO2
atmosphere in order to test the relative importance of volcanism and frost
sublimation in supporting the atmosphere.  This is important for answering
such basic questions as the extent to which the atmosphere collapses at night.
If it does collapse, it is the only substantial atmosphere in the solar system
to behave in this manner.  Our observations will target low-latitude regions
away from active plumes (in contrast to our Cycle 10 observations which
targeted the Prometheus plume), to look for the effect of plumes on the
atmosphere.  We will also look at the variation of low-latitude atmospheric
abundance with  terrain type, to look for explanations for the large
longitudinal variations in atmospheric pressure seen in earlier data.
Finally, we will look at a variety of regions at two different times of day to
determine the extent of diurnal variations in the atmosphere, which are
expected if the atmosphere is dominantly supported by frost sublimation.
================================================================================

Proposal Category:   GO
Scientific Category: SOLAR SYSTEM
ID:                  10270
Title:               Titan : Huygens Probe Entry Fireball and UV Seasonal
                     Change
PI:                  Ralph Lorenz
PI Institution:      University of Arizona

We plan a single-orbit observation of Titan to observe the 387nm CN emission
associated with the entry fireball of the ESA Huygens probe into Titan's
methane-rich nitrogen atmosphere. The observation may confirm the entry  time
of the probe, and provide  constraints on the nonthermal emission from  the
shock  layer and wake for an entry body of known ballistic parameters to  aid
aerothermodynamic models to aid meteoric studies and future heat  shield
designs. Whether the entry is detected or not, the observation also  yields a
north-south spectral profile to diagnose the continuing seasonal  change on
Titan, namely the north-south seasonal asymmetry, and the  disappearing  UV-
dark south polar hood.
================================================================================

Proposal Category:   GO
Scientific Category: HOT STARS
ID:                  10271
Title:               IY UMa: A literal probe of accretion disc structure
PI:                  Carole Haswell
PI Institution:      Open University

IY UMa is a recently-discovered double-lined eclipsing CV with an extremely
high inclination. The orientation allows us a view into a narrow shock-heated
cavity driven into the disc edge by the accretion stream from the mass donor
star. This (literal) probe is so far unique. At the orbital phase when we look
into the hot cavity, the emission from the cavity should be a significant
fraction of the total UV flux. Comparison with our hydrodynamic simulations of
the stream-disc impact will allow us to determine the structure of the cool
quiescent outer disc. We will fully characterise the white dwarf, measuring
its rotation rate, surface gravity, effective temperature, chemical
abundances, accretion rate and gravitational redshift. The obscuration of the
inner UV emitting regions by vertical structure associated with spiral density
waves will be measured and interpreted by comparison with our simulations. The
observations will be performed in the CVZ.
================================================================================

Proposal Category:   SNAP
Scientific Category: STELLAR POPULATIONS
ID:                  10272
Title:               A Snapshot Survey of the Sites of Recent, Nearby
                     Supernovae
PI:                  Weidong Li
PI Institution:      University of California - Berkeley

During the past few years, robotic (or nearly robotic) searches for supernovae
(SNe), most notably our Lick Observatory Supernova Search (LOSS), have found
hundreds of SNe, many of them in quite nearby galaxies (cz < 4000 km/s). Most
of the objects were discovered before maximum brightness, and have follow-up
photometry and spectroscopy; they include some of the best-studied SNe to
date. We propose to conduct a snapshot imaging survey of the sites of some of
these nearby objects, to obtain late-time photometry that (through the shape
of the light and color curves) will help reveal the origin of their lingering
energy. The images will also provide high-resolution information on the local
environment of SNe that are far superior to what we can procure from the
ground. For example, we will obtain color-color and color-magnitude diagrams
of stars in these SN sites, to determine their progenitor masses and
constraints on the reddening. Recovery of the SNe in the new HST images will
also allow us to actually pinpoint their progenitor stars in cases where  pre-
explosion images exist in the HST archive. Use of ACS rather than WFPC2 will
make our snapshot survey even more valuable than our Cycle 9 survey. This
Proposal is complementary to our Cycle 13 archival proposal, in which we
outline a plan for using existing HST images to glean information about SN
environments.
================================================================================

Proposal Category:   GO
Scientific Category: GALAXIES
ID:                  10273
Title:               Accurately Mapping M31's Microlensing Population
PI:                  Arlin Crotts
PI Institution:      Columbia University in the City of New York

We propose to augment an existing microlensing survey of M31 with source
identifications provided by a modest amount of ACS (and WFPC2 parallel)
observations to yield an accurate measurement of the masses responsible for
microlensing in M31, and presumably much of its dark matter.  The main benefit
of these data is the determination of the physical (or "einstein") timescale
of each microlensing event, rather than an effective ("FWHM") timescale,
allowing masses to be determined more than twice as accurately as without HST
data.  The einstein timescale is the ratio of the lensing cross-sectional
radius and relative velocities.  Velocities are known from kinematics, and the
cross-section is directly proportional to the (unknown)  lensing mass.  We
cannot easily measure these quantities without knowing the amplification,
hence the baseline magnitude, which requires the resolution of HST to find the
source star.  This makes a crucial difference because M31 lens mass
determinations can be more accurate than those towards the Magellanic Clouds
through our Galaxy's halo (for the same number of microlensing events) due to
the better constrained geometry in the M31 microlensing situation.
Furthermore, our larger survey, just completed, should yield at least 100 M31
microlensing events, more than any Magellanic survey.  A small amount of
ACS+WFPC2 imaging will deliver the potential of this large database (about 350
nights). For the whole survey (and a delta-function mass distribution) the
mass error should approach only about 15%, or about 6% error in slope for a
power-law distribution.  These results will better allow us to pinpoint the
lens halo fraction, and the shape of the halo lens spatial distribution, and
allow generalization/comparison of the nature of halo dark matter in spiral
galaxies.  In addition, we will be able to establish the baseline magnitude
for about 50,000 variable stars, as well as measure an unprecedentedly
detailed color-magnitude diagram and luminosity function over  much of M31.
================================================================================

Proposal Category:   GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10274
Title:               Prospecting for Rare Elements in the Interstellar Medium
PI:                  James Lauroesch
PI Institution:      Northwestern University

The complex history and evolution of element production is reflected in the
abundance ratios of the elements.  The distinctive abundances patterns
produced by nucleosynthesis in supernovae and stars can be used to explore the
history of star formation and evolution in galaxies.  Recent observations of
damped Lyman-alpha systems have suggested that observations of r and s-process
elements at high redshifts may soon provide a new window to explore chemical
evolution.  Paradoxically, we may soon have more detections of some elements
in the interstellar medium of these high redshift galaxies than in the
Galactic ISM.  However, without an understanding of the depletion behavior of
these elements based upon observations of nearby sightlines we may be unable
to correctly disentangle the effects of dust depletion and nucleosynthesis.
We therefore propose to determine the depletion of r and s-process elements in
two sightlines with relatively mild depletion patterns on nearly opposite
parts of the sky.  In addition to providing a baseline for studies at high
redshift, the long pathlength studied will enable us to search for abundance
variations within our Galaxy.
================================================================================

Proposal Category:   GO
Scientific Category: SOLAR SYSTEM
ID:                  10275
Title:               The Moons, Rings and Arcs of Uranus: Discovery and
                     Dynamics
PI:                  Mark Showalter
PI Institution:      NASA Ames Research Center

Last year, our Uranian ring and moon observing program (GO-9823) resulted in
the discovery of two moons, S/2003 U 1 and S/2003 U 2. We imaged two
additional small moons, Ophelia and S/1986 U 10, that had not been seen since
the Voyager encounter of 1986. Furthermore, our data show faint arcs and
clumps orbiting within the rings, which were not seen by Voyager and are
completely unexpected. We employed several  "tricks" of the HRC to achieve
this remarkable senstivity; specifically, we used the CLEAR filter and
oriented the images so that the planet, though vastly overexposed, did not
interfere with the ring/moon region of interest to us. This allowed us to
detect 25th-magnitude moons circling a 5th-magnitude planet. Now we propose to
complete the task by carrying out a comprehensive survey of the system using
the same techniques. Our goals are to recover the moons, better discern their
orbital elements, and learn more about the dynamics of the ring clumps. In
particular, we need to (1) understand the long-term stability of S/2003 U 2,
which orbits perilously close to the larger moon Belinda; (2) complete our
search for moons, which was only ~ 50% complete last year, and (3) better
understand how the clumps and arcs within the ring system might relate to
nearby "shepherding" moons, seen or unseen.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10276
Title:               Resolving the Distance Ambuguity for the Galactic Open
                     Cluster Westerlund 2
PI:                  Henry Kobulnicky
PI Institution:      University of Wyoming

We ask for 2 orbits with HST/WFPC2 to resolve the distance ambiguity and
characterize the stellar content of the southern Galactic open cluster
Westerlund 2.  Using WFPC2 UBVI imaging, we will catalog its stellar content
down to specral type A0V, determine its age, measure its distance, and thereby
understand the energetics that power the hot diffuse, warm ionized, and photo-
dissociated medium surrounding the cluster.  Westerlund 2 lies at the heart of
the primary calibration field recently observed as part of our Spitzer
Telescope GLIMPSE Legacy survey of the Galactic Plane.  As such, we are
seeking high angular resolution photometry of this crowded stellar field to
probe the nature of the cluster itself and to validate our photometric
analysis of Spitzer imaging in dense Galactic fields.
================================================================================

Proposal Category:   GO
Scientific Category: STELLAR POPULATIONS
ID:                  10277
Title:               Ages and Metallicities of the Intergalactic Globular
                     Cluster Population in Abell 1185
PI:                  Michael West
PI Institution:      University of Hawaii

We request deep NICMOS observations of a recently discovered population of
intergalactic globular clusters in the nearby galaxy cluster Abell 1185.
These H band observations in conjunction with deep V and I images that we
obtained with ACS in Cycle 11 will allow us to measure the ages and
metallicities of these objects from their optical and near-infrared colors,
which will provide important insights to their origin.
================================================================================

Proposal Category:   GO
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID:                  10278
Title:               Probing the Outer Regions of M31 with QSO Absorption
                     Lines
PI:                  David Turnshek
PI Institution:      University of Pittsburgh

We propose HST-STIS-UV spectroscopy of 10 recently-discovered quasars behind
M31. Absorption lines due to MgII and FeII will be searched for and measured.
Six quasars lie between 1 and 4.2 Holmberg radii near the major axis on the
southwest side, where confusion with Milky Way gas is minimized. Two lie even
farther out on the southwest side of the major axis. One lies within 1
Holmberg radius. Two of the 10 pass through M31's high velocity clouds
recently seen in a detailed 21 cm emission map. Thus, using the most well-
studied external spiral galaxy in the sky, our observations will permit us to
check, better than ever before, the standard picture that quasar metal-line
absorption systems arise in an extended gaseous halo/disk of a galaxy well
beyond its observable optical radius. Notably, the observations have the
potential of extending M31's rotation curve to very large galactocentric
distances, thereby placing new constraints on M31's dark matter halo.
================================================================================

Proposal Category:   AR
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10279
Title:               A Comprehensive Study of Interstellar Depletions
PI:                  Edward Jenkins
PI Institution:      Princeton University

We propose to analyze interstellar gas-phase abundances of Ga, Sn, Pb, B, S by
measuring their absorption features in the spectra of stars observed in SNAP
survey programs 8241, 8662 and 9434 (plus other programs that have had archive
data  released to the public).  The lines of Pb II and B II are extremely
weak, so stars will be grouped into cases having different levels of general
depletion and then within each category the spectra will be coadded to enhance
the detectability of the lines.  These data will be combined with results
derived by S. Cartledge and coworkers on O and Kr, plus data soon to be
published for Ge, Cu, Mg, Mn, Ni and P,  in order to understand the general
behavior of depletions of atoms onto dust grains under different conditions,
using a new analysis technique developed by Jenkins (2003).  A better
knowledge of the systematics of depletions will be beneficial to studies of
the compositions of dust grains and will also aid investigations of total
element abundances in distant damped L-alpha (DLA) systems seen in the spectra
of quasars recorded by ground-based telescopes.
================================================================================

Proposal Category:   AR
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10280
Title:               Fundamental Properties of Gas in the Distant Galactic
                     Halo and Leading Arm of the Magellanic Stream
PI:                  Todd Tripp
PI Institution:      University of Massachusetts

We propose to use high-resolution archival STIS echelle spectra of a cloud
that is located in the Magellanic Stream, and therefore at a distance of ~50
kpc, to obtain detailed observational constraints on the density, pressure,
temperature, and ionization structure of gas in the leading arm of the
Magellanic Stream. Since this cloud is known to be pressure-confined by the
surrounding halo gas, the results will have implications for the physical
conditions of the Galactic halo as well. We will apply the following
diagnostics to the absorption lines in archival STIS spectra: (1) thermal
pressure from C I fine-structure excitation, (2) density constraints from C
II*, (3) electron density and temperature from ionization balance, and (4)
ionization structure and density constraints from photoionization models. With
these physical conditions measurements, we will learn about the nature of O
VII and high-velocity O VI absorbers, the evolution of satellite galaxies that
pass close to the Milky Way, and whether theoretical work on the ISM in the
Milky Way halo agrees with observations.  We will also learn about
production/destruction of molecular hydrogen in conditions similar to the
high-z conditions in which early stars formed.
================================================================================

Proposal Category:   AR
Scientific Category: STELLAR POPULATIONS
ID:                  10281
Title:               Evolution of Stars and Stellar Systems. I. The Initial
                     Size Distribution of Clusters
PI:                  Rupali Chandar
PI Institution:      Space Telescope Science Institute

There are three fundamental properties which define a star cluster -- age,
mass, and size.  While much attention has been focused on the first two
parameters, significantly less is known concerning not only actual cluster
sizes and structures, but the initial distribution of stellar clustering which
occurs in different environments.  For example, NGC 1569 has formed three
compact, massive young clusters in the last 10 Myr, while IZw18 appears to
have only formed more diffuse, "scaled up" OB associations (SOBAs).  The HST
archive now contains sufficient observations of nearby star-forming galaxies
to allow a quantitative measure of the initial clustering of star formation.
We propose to measure the distribution of the physical scales of cluster
formation, from the most compact clusters to diffuse SOBAs in 30 nearby
galaxies.  Local variations in the star formation rate may manifest themselves
in the fraction of star formation occuring in compact clusters vs. that
occurring in more diffuse OB associations.  Because our galaxy sample covers a
large range in environment, mass, and star formation rate density, we will
take the next step, and use our size distributions to place constraints on the
processes responsible for setting the scales of star formation in the local
universe.  A complementary proposal aims to study the isolated red supergiant
population in nearby star-forming galaxies (PI: Dr. C. Leitherer).
================================================================================

Proposal Category:   AR
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID:                  10282
Title:               Discovery of two Star-Forming Galaxies causing strong
                     Quasar Absorption Lines
PI:                  Regina Schulte-Ladbeck
PI Institution:      University of Pittsburgh

We have positionally matched our database of over 19,000 star-forming galaxies
(SFGs) from the Sloan Digital Sky Survey (SDSS) against the SDSS QSO catalog.
This has allowed us to discover nineteen bright QSOs with redshifts of less
than or about one behind local SFGs. Two of the QSOs were fortuitously already
observed with HST, and show strong Lyman alpha lines at the emission-line
redshifts of the SFGs
================================================================================

Proposal Category:   AR
Scientific Category: COSMOLOGY
ID:                  10283
Title:               Confronting HST Observations of Dwarf Spheroidals with
                     Theory
PI:                  Nickolay Gnedin
PI Institution:      University of Colorado at Boulder

We will continue our work on using advanced cosmological simulations to model
the formation and evolution of dwarfs spheroidal galaxies. Our previous
simulations were able to fully resolve the internal structure of dwarf
spheroidals formed before the reionization epoch. In this cycle we will
incorporate results from our previous simulations into a large-scale N-body
only code to model the formation of the Local Group and to relate the results
of our gas-dynamical simulations to the present distribution of dwarf
spheroidals in the Local Group. The results of our simulations will be
compared to the observational data, including the color-magnitude diagrams of
dwarfs spheroidals, obtained by the HST.
================================================================================

Proposal Category:   AR
Scientific Category: AGN/QUASARS
ID:                  10284
Title:               Formation of Structure in AGN Accretion Disk Winds:
                     Theory and Observational Implications
PI:                  Isaac Shlosman
PI Institution:      University of Kentucky

HST observations of UV emission- and absorption-line spectra in AGN indicate
the presence of highly structured outflows, characterized by complex large-
scale flow patterns and small-scale clumpiness. These outflows are best
explained as winds coming off accretion disks around supermassive black holes,
propelled and shaped by a combination of line-radiation pressure and
hydromagnetic forces. We propose to make the first comprehensive study of
hybrid radiative/hydromagnetic winds in the context of AGN flows. We will
particularly focus on a new class of instabilties, "radiative-
magnetoacoustic'' modes, that show great promise for explaining both the
global properties of the winds (velocity fields, mass loss rates) as well as
the small-scale clumpiness. Our results will be fed into a 3D radiative
transfer code to compute synthetic BEL and BAL line profiles, to study their
time and shape variability, that can be directly compared with existing (and
future) HST observations of AGN.
================================================================================

Proposal Category:   AR
Scientific Category: HOT STARS
ID:                  10285
Title:               Accreting White Dwarfs and Neutron Stars Near the
                     Galactic Center
PI:                  Mark Morris
PI Institution:      University of California - Los Angeles

We propose to analyze NICMOS observations of the central 5 pc of the Milky Way
Galaxy in order to identify the nature of X-ray sources recently detected in a
deep set of Chandra observations. We plan to determine the relative numbers of
high-mass X-ray binaries with characteristic ages of 10^7 years, and
magnetically accreting cataclysmic variables with ages of over 10^9 years. The
results will provide information about the recent star formation history, the
propensity for binaries to form, and the mass of stellar remnants at the
Galactic center.
================================================================================

Proposal Category:   AR
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID:                  10288
Title:               The astrophysics of the intergalactic medium at
                     intermediate redshifts
PI:                  David Kirkman
PI Institution:      University of California - San Diego

We will use the 334 low resolution FOS spectra and the 31 STIS spectra already
in the archive to determine the properties of the 0.3 < z < 2 IGM.  All of the
mentioned spectra are of bright QSOs and cover part of the Lyman alpha forest.
We will compute traditional line statistics, but more importantly we will
compute a number of pixel statistics using the same analysis methods used by
groups that simulate the Lyman alpha forest.  Examples of the pixel statistics
include the flux power spectrum, the distribution of flux per pixel, and the
mean flux decrement of the Lyman alpha forest.  The results will enable for
the first time a detailed comparison between data and theory at z < 1.7.
Specific scientific issues that will be addressed with the results of this
research include (1) The spatial structure of the IGM, (2) The thermo-
dynamical state of the IGM, (3) The intensity and evolution of the UV
background, and (4) The effects of galaxy feedback on the IGM.
================================================================================

Proposal Category:   AR
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10289
Title:               The Astrophysics of Heterogeneous ("Clumpy") Stellar
                     Outflows
PI:                  Adam Frank
PI Institution:      University of Rochester

HST imaging has revealed many circumstellar environments to consist of highly
inhomogeneous media. The presence of such "clumpy" mass distributions will
have significant consequences for large-scale flows such as mass loss from
young and evolved stars as well as strong shocks propagating through
interstellar clouds.  While clumping can cause dramatic changes in the
properties of such flows there remains a fundemental gap between the
relatively few theoretical studies of large scale clumpy flow systems and
observational interpretations.  In this proposal we outline a theoretical
study of clumpy flows in circumstellar outflows using a new, advanced adaptive
mesh refinement numerical code known as AstroBEAR. This tool is being
developed to handle multi-physics astronomical phenomena (situations in which
many physical processes such as magnetic fields, ionization, chemistry, and
radiation transport must be simultaneously simulated). Our study will provide
unparalleled resolution to study the radiative gasdynamic, magneto-gasdynamic
and photo-ionization evolution of heterogeneous flows. The code will track
ionization and micro-physical states in the flow allowing detailed comparison
with HST observations of YSO jets and Planetary Nebulae.  We plan to apply the
code to the observations of clumpy bow shocks and internal working surfaces in
HH 1-2, HH34, and HH46/47.  We will also conduct studies relevent to the
stellar wind blown bubble PNe systems NGC 2392 and NGC 6751.
================================================================================

Proposal Category:   AR
Scientific Category: GALAXIES
ID:                  10290
Title:               Constraints on galaxy formation models from size
                     evolution of galactic disks and spheroids
PI:                  Rachel Somerville
PI Institution:      Space Telescope Science Institute

The radial sizes of disks and spheroids are fundamental properties of
galaxies, and must be connected with the efficiency of star formation,  yet
neither numerical nor semi-analytic galaxy formation models are currently able
to model them accurately.  We propose to compile measurements of disk and
spheroid sizes from the Sloan Digital Sky Survey (SDSS), Great Observatories
Origins Deep Survey (GOODS), and GEMS (Galaxy Evolution from Morphology and
SED) survey to characterize in a single consistent analysis the evolution of
galaxy sizes from z=5 to the present. We will confront these observations with
predictions from three different paradigms of galaxy evolution: (1) a no-
evolution model (2) a backwards-evolution model and (3) a hierarchical model
based on semi-analytic techniques. For (3), we will develop new physically
motivated modeling of the sizes of disks and spheroids, which has not
previously been done self-consistently in a semi-analytic model set within the
complete framework of the Cold Dark Matter merging hierarchy. We will account
for the formidable selection and measurement biases and cosmic variance by
creating synthetic images based on each model paradigm, and running the actual
object detection and structural fitting software on these images to create
mock catalogs of "observed" galaxy properties.  We will use Bayesian methods
to quantify the parts of parameter space that are favored within each
paradigm, and to assess which model paradigm is favored overall by the data.
By carrying out this program, we hope to gain insight into the physical origin
of observed galaxy sizes and fundamental scaling relations and their evolution
through cosmic history.
================================================================================

Proposal Category:   AR
Scientific Category: GALAXIES
ID:                  10291
Title:               The Distribution of Stars Around the Massive Black Hole
                     at the Galactic Center
PI:                  Farhad Yusef-Zadeh
PI Institution:      Northwestern University

We believe that the Galactic center provides the best opportunity for
investigating the distribution of stars and gas in the immediate vicinity of a
supermassive black hole, at a level of detail that will not be accessible in
any other galactic nucleus. We propose to utilize approximately 150 HST NICMOS
archival images to investigate the nature of the surface brightness
distribution within the inner few tens of arcseconds of the Galactic center.
In particular, we will examine the claim that there is a deficiency of stars
within the inner 1 arcsecond of Sgr A*. This could be evidence of the core
radius of the nuclear stellar distribution or it might be due to the depletion
of late-type stars with high mass-to-light ratios. Yet another possibility is
ejection of stars from the central 1 arcsecond by a past or present binary
black hole.
================================================================================

Proposal Category:   AR
Scientific Category: STELLAR POPULATIONS
ID:                  10292
Title:               Theoretical Studies of the Cores of Globular Clusters
PI:                  Gordon Drukier
PI Institution:      Yale University

HST observations of globular cluster cores have resulted in many radial-
velocity and proper-motion data sets, with the potential for many  more. These
have led to various claims for the existence of intermediate-mass black holes
in some globular clusters. The theoretical underpinning of these claims is
very weak, however. We propose to produce new models of globular cluster
cores, both with and without black holes, in order to redress this lack and
allow us to make the most effective use of the HST data.
================================================================================

Proposal Category:   AR
Scientific Category: COSMOLOGY
ID:                  10293
Title:               The Assembly History of Disks and Bulges out to z=1
PI:                  Richard Ellis
PI Institution:      California Institute of Technology

We propose to exploit the unique set of ACS multi-color images in the Northern
GOODS field in conjunction with a new ground-based database of infrared
photometry and high quality Keck spectroscopy.  The overall goal is to
correlate the dynamical and photometric properties of disks and bulges in the
context of popular models for galaxy assembly. The resolved colors and
physical scales of bulges in the redshift range 0.3100 z=1 disks will be analyzed
with extended rotation curves to address the important question of whether
stellar disks were mature and established at early epochs. The program
represents a concerted attempt to address the origin of key components which
form the basis of the Hubble sequence of galaxies.
================================================================================

Proposal Category:   AR
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10294
Title:               The SN 1987A/LMC "Deep Field"
PI:                  Stephen Lawrence
PI Institution:      Hofstra University

We propose to astrometrically register and co-add the complete archive of
WFPC2 PC-chip imaging centered on SN 1987A, creating a "SN 1987A Deep Field."
These data span 16 epochs between 1994 Feb and 2002 May in six broad-, one
medium- and three narrow-band filters with total exposure times ranging from
1.3--11.4 hours. This dataset will be used to: 1) map out the faintest line-
emitting structures in the photoionized bipolar circumstellar nebula
surrounding SN 1987A, 2) generate fading lightcurves and [OIII]/(H-
alpha+[NII]) line emission maps of the various component substructures of this
nebula, 3) establish a highly-accurate astrometric grid of stars within 20
arcseconds of SN 1987A, 4) generate very deep (m~25.5--26.5) broad-band
photometry of these same LMC field stars, and 5) identify any variable stellar
sources in the field.  Additionally, we would seek to register and stack the
surrounding WF chip images, extending the stellar and ISM field out to 2
arcminute radius.  Once we have accomplished our goals we will make these
images publically available.  Further science that would be available from
these publicly-released deep field images includes: 1) a deep map of LMC
interstellar line emission unrelated to SN 1987A, which can be correlated with
other imaging and spectroscopic datasets, 2) a small, but deeper, set of
stellar photometry than currently exists in this field from which stellar
population, IMF and extinction studies can be done, and 3) a sample of
variable stars and other stellar types potentially useful as distance
estimators.
================================================================================

Proposal Category:   AR
Scientific Category: SOLAR SYSTEM
ID:                  10295
Title:               The Escape of Oxygen from Mars
PI:                  Jody Wilson
PI Institution:      Boston University

This proposal is to perform detailed analysis of STIS observations of the
upper atmosphere of Mars, using an ionospheric model, general circulation
model results for the neutral atmosphere, and various recent spacecraft
observations of Mars.  The end goal is to better understand the escape of
oxygen, and by extension water, from Mars. The observations have yielded limb
profiles of atomic hydrogen, atomic oxygen, and carbon monoxide with 24 km
vertical resolution and a field of view that is thousands of km long. Most of
the hydrogen and some of the oxygen atoms thus detected are escaping from
Mars. There are no other measurements of volatiles escaping from Mars with
nearly such high spatial resolution and large field of view. The data analysis
in the original observing proposal will derive spatially-averaged escape rates
of hydrogen and possibly oxygen at the time of the observations. This archival
research will go beyond that analysis by investigating how the escaping
species diffused through the upper atmosphere to reach the exobase and
relating these observations of current escape rate to the time history of
escape. The escape of water from Mars has had a major impact on its climate
history, the understanding of which is a major scientific goal of NASA's
Office of Space Science.
================================================================================

Proposal Category:   AR
Scientific Category: AGN/QUASARS
ID:                  10296
Title:               Searching for Quasar-Intrinsic Absorption Through Time
                     Variability
PI:                  Rajib Ganguly
PI Institution:      Space Telescope Science Institute

We propose to use multi-epoch, low-resolution spectra of quasars from the HST
archive to look for narrow absorption lines that exhibit time variability.
This is an economical test for identifying absorbers that are intrinsic to the
quasar central engine, and also provides constraints on the density an/or
location of the gas. Narrow absorption lines (NALs) which appear in the
spectra of quasars are very powerful tool to diagnose the physical conditions
(e.g., ionization, geometry) from a variety of structures, ranging from the
ISM of the Galaxy, to the central engine of the quasar. The primary signatures
that distinguish intrinsic NALs from intervening NALs are partial coverage of
the background source and time variability. The former requires high spectral
resolution which can be observationally expensive.  We have completed a pilot
study using associated NALs (those which appear near the quasar redshift) and
have devised an approach to efficiently select time-variable absorption using
multi-epoch spectra from different instruments. We wish to expand our search
to the ~100 quasars that have archived multi-epoch low-resolution spectra.
The quasars span a large range of redshifts and luminosity, and the proposed
study will allow us to select low- and high-velocity intrinsic NALs.
Furthermore, we can decipher the underlying cause of the variability - bulk
motion of the gas, or ionization changes - which have differing observational
signatures.
================================================================================

Proposal Category:   AR
Scientific Category: STELLAR POPULATIONS
ID:                  10297
Title:               The Local Environments of Supernovae
PI:                  Schuyler Van Dyk
PI Institution:      California Institute of Technology

The locations of supernovae (SNe) in the local stellar and gaseous environment
in galaxies, as measured in high spatial resolution WFPC2 and ACS 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 population, setting constraints on the mass of the progenitor,
we  can also search for possible attenuation of the SN by dust in the host
galaxy by studying the colors of the stars in its environment. 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; as
the number of archival HST images steadily increases, along with the number of
newly discovered SNe, positive identifications become progressively more
likely. In Cycle 13, we plan to extend our successful work from previous
cycles. A major improvement is that very good ground-based coordinates are now
available for numerous recent SNe.
================================================================================

Proposal Category:   AR
Scientific Category: GALAXIES
ID:                  10298
Title:               Structural Evolution of Galaxies with GOODS and the
                     Ultra-Deep Field
PI:                  Seth Cohen
PI Institution:      Arizona State University

We propose to study the evolution of the internal structure of galaxies for
z<2. We will use existing ACS archival data from the two GOODS fields, along
with the Hubble Ultra-Deep Field (UDF). We will take maximal advantage of
image depth and resolution, and use all four BVi'z' bands along with the
wealth of available spectroscopic and photometric redshifts in these fields.
We propose to:  (1) Utilize our U-band database of over 300 nearby galaxies of
all types and inclinations to calibrate quantitative structural measurements
of these ACS images of galaxies with z<2 and take advantage of the multiband
aspect of the Archival ACS data.  (2) Apply a fully two dimensional Fourier
Decomposition technique to quantify the existence of structural features
(types of spiral features and bars or lack thereof) as a function of redshift
to trace to formation of the present day Hubble sequence.   (3) Use the deeper
UDF images to study the reliability of such measurements over the wider GOODS
fields and to push these measurements to fainter flux levels only where it can
be justified using what is learned in (1).  (4) Produce and distribute a
catalog of our results.
================================================================================

Proposal Category:   AR
Scientific Category: GALAXIES
ID:                  10299
Title:               Morphological analysis of z=5.7 Lyman Alpha sources in
                     the GOODS/UDF fields
PI:                  Norbert Pirzkal
PI Institution:      Space Telescope Science Institute

We propose to carefully measure the morphology of z=5.7, narrow band selected
Lyman Alpha  emitters in the GOODS-S and UDF fields. The candidate objects
will be selected using existing observations of these fields taken from the
ground, under sub arcsecond seeing conditions, and using two narrow band
filters (823 nm and 815nm). While the number of detections of  high redshift
Lyman Alpha  sources has been steadily increasing in the past year, very
little is known about the source of the Lyman Alpha  emission. The observed
high Lyman Alpha  equivalent widths of these objects have been explained using
a variety of scenarios such as extreme youth of the stellar population, zero
metallicity objects, energetic winds or type II quasars. Studying the
morphology of these objects should provide us with a unique opportunity to
differentiate between several processes believed to be behind the observed
Lyman Alpha  emission. Recently, and soon to be made, public HST ACS
observations of the GOODS/UDF fields, with their high angular resolutions and
its well calibrated, stable PSF provide us with a unique opportunity to study
the clumpiness and  spatial extension of these objects.
================================================================================

Proposal Category:   AR
Scientific Category: COSMOLOGY
ID:                  10300
Title:               Properties of moderate-redshift galaxy groups associated
                     with gravitational lenses
PI:                  Christopher Fassnacht
PI Institution:      University of California - Davis

Strong evidence indicates that the primary lensing galaxies in many
gravitational lens systems are associated with compact groups.  We are taking
advantage of this association to conduct an active ground-based program to
find galaxy groups at moderate redshifts.  Because the lens galaxies are
typically in the redshift range of 0.3 1 in the COSMOS Field
PI:                  Lin Yan
PI Institution:      Jet Propulsion Laboratory

We propose to identify the population of extremely red galaxies (EROs) in the
COSMOS treasury dataset, by combining the primary F814W images with their
NICMOS F160W parallels.  COSMOS parallels with NICMOS provide an unprecedented
combination of extraordinary depth (Vega=24), area coverage (200 sq. arcmin)
and spatial resolution.  The ERO selection will be limited by the F814W depth,
so the entire red galaxy sample will consist of high significance detections
suitable for quantative morphological analysis.  We will measure the surface
density of red galaxies (I-H > 3) fainter than current ground-based surveys
can detect in order to determine whether the counts flatten beyond H=20.5. We
will establish whether the large disk fraction (60%) seen in the optical holds
true in near-infrared morphologies.  And we will determine whether ERO
clustering strength has any morphological dependence.
================================================================================

Proposal Category:   AR
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID:                  10304
Title:               Departures from Axisymmetry in Planetary Nebulae
PI:                  Matthew Bobrowsky
PI Institution:      Computer Sciences Corporation

It is well known that outflows from planetary and proto-planetary nebulae
often exhibit axial symmetry. What is less well known are the *departures*
from axial symmetry, which need to be investigated if we are to have a
complete understanding of how planetary nebulae form and evolve. A study of
the departures is very timely, as 3D hydrodynamic numerical simulations are
now being developed. The HST archive contains ~3000 exposures of >400
different galactic planetary or proto-planetary nebulae. By measuring the
departures from axisymmetry for these targets, we will learn how the
departures are related to, and caused by, the physical and dynamical
conditions of the nebulae and central stars. We will produce a catalog for the
community that includes classifications and comparisons of the departures, and
correlations with physical and dynamical properties. We will apply our results
to departures from axisymmetry observed in PNe and in other types of objects,
e.g., SN 1987A, Eta Carinae. We have measured asymmetries for a few sample
objects; so we know we will obtain reliable, quantitative results that we (and
others) will use to understand the origin of the departures from axisymmetry
in a variety of objects. Long after our work on this project ends, the catalog
of PN parameters will continue to benefit the wider community.
================================================================================

Proposal Category:   AR
Scientific Category: AGN/QUASARS
ID:                  10305
Title:               Outflows from Seyfert galaxies: a challenge to current
                     models
PI:                  Daniel Proga
PI Institution:      University of Colorado at Boulder

We propose to continue our study of outflows from active galactic nuclei
(AGN).  This phenomenon has been extensively observed with HST as well as
modeled.  The overall result from previous studies, including our own ongoing
HST program,  is that broad absorption lines (BAL) in QSOs can be well
understood and reproduced  within the framework of radiation-driven disk wind
models. It is also very likely that  the same model is capable of explaining
broad emission lines. However, this model is  less successful in explaining
narrow absorption lines (NAL) observed in Seyfert galaxies. Therefore, we
propose to extend the model by including magnetic field effects.
Hydromagnetic propulsion is a likely mechanism responsible for producing low
velocity outflows from larger radii and thus explaining NAL and their lack of
short-term variability.  We will continue to use the multi-dimensional, time-
dependent, magnetohydrodynamical code ZEUS to compute the wind structure. We
will also compute synthetic line profiles  and continuum spectra based on the
theoretical model  and compare the results with  HST/STIS and other
observations. In general, we propose to follow the procedure  which we
successfully applied  to winds in cataclysmic variables and BAL QSOs.
================================================================================

Proposal Category:   AR
Scientific Category: GALAXIES
ID:                  10306
Title:               Archival Study of Merger-Induced Populations in Early-
                     Type Galaxy Cores
PI:                  Jodie Martin
PI Institution:      The University of Virginia

Hierarchical formation models predict that early-type galaxies are built up
over an extended period from mergers of smaller systems, a process which
should leave long-lived signatures in their light profiles and stellar
population colors.  Merger events should have continued up to relatively
recent times (the last 1-5 Gyr), and many ellipticals and S0 bulges should
therefore show evidence of multiple, discrete, intermediate-age populations.
Although there is substantial observational support for a dissipational merger
origin for some early-type galaxies, most do not exhibit the expected
anomalies in either their light profiles or color distributions.  However,
existing searches have primarily been monochromatic and those which used
multi-bands studied only narrowly defined subsamples of early-type galaxies.
Here we propose an archival study of high resolution, broad-band, multi-color
images of the cores of a large sample of 167 early-type galaxies which are
representative of the general population.  This is the most extensive search
intended to probe spatially-segregated, multiple population components with
ages in the range 1-5 Gyr.  Our sample consists of early-type galaxies in a
wide range of environments from the field to groups to rich clusters.  There
is very little information on the color structure of core stellar populations
of early-type galaxies in different environments and how they may relate to
gaseous merger histories and our program would effectively explore new
terrain.  Simulations of mergers show that gas generally falls deep into the
potential well to scales within a few 100 pc of the center before forming
stars.  An effective search for distinct populations must therefore be able to
resolve these scales, which is possible for a meaningfully large sample only
with HST.
================================================================================

Proposal Category:   AR
Scientific Category: STELLAR POPULATIONS
ID:                  10307
Title:               Photo- and Spectro-Chemical Evolution Models for
                     Starburst Galaxies
PI:                  Gerardo Vazquez
PI Institution:      Space Telescope Science Institute

We propose to develop new chemically consistent evolutionary synthesis models
for young stellar populations containing massive stars, including Wolf-Rayet
stars. Such populations are the powering sources of starburst galaxies at low
and high redshift and are major chemical pollutants of the interstellar and
intergalactic medium. The new models are based on the successful Starburst99
code, which will be expanded to allow for stellar evolution at arbitrary (not
discrete) chemical composition, including metallicity zero. We will supplement
our current grid of stellar models by newly developed evolutionary tracks with
rotation. The chemical evolution models will not make the instantaneous
recycling approximation and will account for infall and outflows. Existing
chemical evolution models do either have to rely on these assumptions or, if
they do not, their adopted stellar models make them inapplicable to young
massive populations.
================================================================================

Proposal Category:   AR
Scientific Category: COSMOLOGY
ID:                  10308
Title:               SLACR: The Simulation Lyman Alpha Comparison Repository
PI:                  Romeel Dave
PI Institution:      University of Arizona

I propose to establish SLACR, the Simulation Lyman Alpha Comparison
Repository.  SLACR is a publically-accessible full-service website containing
the data and software tools necessary to generate and analyze artificial Lyman
alpha forest spectra drawn from state-of-the-art cosmological hydrodynamic
simulations.  These artificial spectra can be analyzed alongside ultraviolet
quasar and AGN spectra taken using e.g. HST/STIS, in order to (1) Test current
theories of the IGM; (2) Constrain the physical state of absorbing gas seen in
quasar spectra; (3) Assess biases and uncertainties due to sample
incompleteness, continuum fitting, and Voigt profile fitting; (4) Constrain
physical and cosmological parameters of the IGM from absorption line data; and
(5) Study the relationship between IGM absorbers and large-scale structure as
traced by galaxies.  SLACR will be an invaluable model comparison and data
interpretation tool for HST observers studying the Lyman alpha forest,
associated metal absorption systems, "missing baryons" and the warm-hot
intergalactic medium, and galaxy-absorber correlations.
================================================================================

Proposal Category:   AR
Scientific Category: GALAXIES
ID:                  10309
Title:               The Globular Cluster Systems of Low Mass Spiral Galaxies
PI:                  Anil Seth
PI Institution:      University of Washington

We propose to study the globular cluster systems of approximately twenty edge-
on, low mass, late type spiral galaxies using archival ACS snapshot data.
This sample of galaxies falls in a range of masses and morphologies neglected
by previous studies.  Analysis of this sample will enable us to study
variations in globular cluster system properties and their correlation with
galaxy mass and morphology.  Specifically, we will be able to address the
correlation of metal-rich clusters with bulge mass, the possible increase of
specific frequencies at lower galaxy masses and the galaxy mass dependence of
globular cluster destruction mechanisms.
================================================================================

Proposal Category:   AR
Scientific Category: GALAXIES
ID:                  10310
Title:               Windows of the Early Universe beyond Redshift 7
PI:                  Wei Zheng
PI Institution:      The Johns Hopkins University

Deep ACS images such as UDF are our most powerful probe of the early universe
to date, with the discovery of many z~6 candidates. Thousands archival ACS
images  have covered areas whose sum  is significantly larger than the GOODS
fields, providing an ideal opportunity to further search for objects at z>7,
characterized as z-band "dropouts."  We will carry out a systematic search of
these objects by combining multi-band ACS images, with deep ground-based
infrared photometry.  Our goals are:  (1) Discovery of (bright) z>7 galaxies,
to probe the reionization epoch of the intergalactic medium;  (2) Study of the
luminosity function of galaxies at z>6. The results  will provide insight into
the z>10 universe, particularly the bright end of the source distribution,
which is crucial for the JWST.
================================================================================

Proposal Category:   AR
Scientific Category: GALAXIES
ID:                  10311
Title:               The Physical Nature of Galaxy Morphology During the Peak
                     Epoch of Galaxy Formation
PI:                  Charles Steidel
PI Institution:      California Institute of Technology

We propose to use the deep ACS images obtained by the Great Observatories
Origins Deep Survey (GOODS) in combination with a sample of ~300
spectroscopically identified galaxies with 1.46)
or if this formation was delayed up to z~1-2 by the intense UV-radiation field
present at higher redshifts.  The depth and high spatial resolution of the UDF
are required in order to detect the low-surface-brightness stellar population
associated with the galaxy halo and to separate and spatially resolve it from
the central, high-surface-brightness component.
================================================================================

Proposal Category:   AR
Scientific Category: SOLAR SYSTEM
ID:                  10322
Title:               Electron Impact Simulations of Io's Atmosphere
PI:                  Laurence Trafton
PI Institution:      University of Texas at Austin

August 1999 HST/STIS observations of Io in Jupiter's shadow by Bagenal et al.
(Program 8169) revealed 1700-5000 A emission from SO2, SO, and S I that was
attributed to impact excitation/dissociation by plasma torus thermal
electrons. The conclusions of their analysis were limited by their simplified
model of Io, necessitated by the lack of laboratory data and information on
the complex geometry of Io's patchy atmosphere and volcanoes. Since then, many
Galileo observations of Io have been published which make a detailed model
atmosphere for this epoch possible with few free parameters.  In addition,
laboratory experiments have better-defined both the electron-impact and NUV
absorption cross-sections of SO2. Meanwhile, we have developed the capability
to simulate the emission from the interaction of plasma particles with Io's
neutral atmosphere, overlaying a radiation code onto our 3-D Monte Carlo flow
field model of Io without making any of the unrealistic approximations of the
original analysis (i.e., uniform isothermal atmosphere; no energy lost by the
exciting electrons; and no absorption by SO2). We propose to use these
spectral images to constrain the remaining free parameters of this simulation
to yield column abundances and atmospheric electron densities on the Jupiter-
facing side of Io.  The atmospheric S/SO2 abundance ratio is a diagnostic of
SO2 dissociation in the internal volcanic magma that would constrain the
volcanic process.  These eclipse observations are unique; and they constrain
models of Io's molecular atmosphere in ways no other extant data can.
================================================================================

Proposal Category:   AR
Scientific Category: STELLAR POPULATIONS
ID:                  10323
Title:               ORIGIN OF THE GLOBULAR CLUSTER FUNDAMENTAL PLANE
PI:                  Dean McLaughlin
PI Institution:      Space Telescope Science Institute

HST has provided many revolutionary new insights on the existence, formation
and properties of star clusters in the Universe. One of the most important
findings has been that star formation in almost any environment involves the
formation of massive stellar clusters which look very much like what is
expected of halo globular clusters when they were young. This discovery has
rejuvenated ideas about globular cluster formation and star formation in
general. Nonetheless, our understanding of the globular cluster formation
process remains woefully incomplete. Although the integrated properties of
globular clusters in external galaxies have long been studied from the ground,
only with Hubble has it become possible to resolve the interiors of individual
clusters in the halo of M31 and more distant galaxies. This has shown that
globular clusters always have the same typical half-light radius of about 3
pc. This generalizes earlier findings for Milky Way clusters to a wide range
of galactic environments and metallicities. Even more, with Hubble it is
becoming increasingly clear that the same is true for young massive clusters.
Phrased differently, the properties of clusters of all types define a
remarkably uniform fundamental plane. While the ubiquity of this plane becomes
clearer with every new Hubble observation, it remains a mystery what processes
during cluster formation regulate its existence. It is also not understood why
clusters (size independent of mass) and galaxies (size increases with mass)
follow such different scaling relations. We will target these questions with a
theoretical study of cluster formation. Using a semi-analytical approach we
will study which processes and parameters are the driving force behind the
observed relations. Theoretical work is badly needed to provide a coherent
framework for the interpretation of the many important cluster results that
Hubble has provided. Our study is therefore ideally suited for the Hubble
Theory Program.
================================================================================

Proposal Category:   AR
Scientific Category: COSMOLOGY
ID:                  10324
Title:               The Morphology of Ly-alpha Emission Galaxies at z=3.11 in
                     the GOODS-S Field
PI:                  Caryl Gronwall
PI Institution:      The Pennsylvania State University

The discovery of large numbers of Lyman-break galaxies has revolutionized our
ability to study the distant universe.  Today, narrow-band surveys have
finally caught up and are detecting Ly-alpha emission-line galaxies (ELGs)
from z=2.4 to z=6.5. These are important objects:  not only do they sample a
part of the galaxy luminosity function that is inaccessible to the Lyman-break
technique, but they also tend to be younger and less chemically evolved.  As a
result, these ELGs present us with a unique opportunity to study galaxies in
the process of formation. We have performed several ground-based narrow-band
surveys for ELGs at z~3.1, including one centered on the Chandra Deep Field
South.  Spectroscopy has confirmed that our objects have broad (~450 km/s),
asymmetric line profiles, consistent with that of a starburst galaxy.    We
propose to use archival HST ACS WFC observations of the Chandra Deep Field
South from the GOODS treasury program to study the morphology of Ly-alpha ELGs
at z=3.11.  Our recent ground-based survey of this field contains about 10 Ly-
alpha ELGs within the GOODS ACS WFC pointings.  The F775W and F850LP images
will detect the objects'  rest-frame UV continuum, and allow us to measure
their structure on sub-kpc scales.  With these data we can probe the physical
nature of these distant objects and derive important new insights on the
nature of galaxy formation.   In addition, we will directly compare the
properties of our ELGs to similar objects found at higher redshift (4 < z <
7), and to the Lyman-break galaxies contained in the field.   This sample is
an important lower redshift counterpart to recent discoveries of Ly-alpha ELGs
at higher redshift (z = 4 - 7).  In addition, we will be able to directly
compare the properties of the emission-line sources to Lyman-break galaxies at
the same redshift in the same field discovered by the GOODS team.
================================================================================