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: http://hea-www.harvard.edu/REU/projects05.html
Дата изменения: Unknown Дата индексирования: Mon Oct 1 20:54:36 2012 Кодировка: Поисковые слова: blue stragglers |
------- Advisor's project abstract:
We have Magellan spectra of many stars in globular
clusters and in the field that can be used to
determine (or put limits on) the rotation rates of the
stars. A template spectrum
will be developed (using spectral synthesis codes), the
appropriate template will be used to compare to line
widths of stars in several globular clusters of different
metallicities. Other features of the spectrum can be used
as well to correlate rotation with mass loss, H-alpha
emission, Ca K emission etc.
The project will involve working with existing codes,
along with standard software/editing packages: iraf,
idl, latex. Literature research will also be needed.
------- Student's final abstract:
J. L. Blum (CfA), A. K. Dupree (CfA),
I. I. Ilyin (Astrophysical Institute Potsdam),
\& D. D. Sasselov (CfA)
The He I 10830{\AA} line in the spectra of cool luminous stars,
can reveal the dynamics of the chromosphere because the
line-forming process is independent of local conditions.
Following photoionization of neutral helium by the star's X-ray
and EUV flux, helium recombines into a metastable state.
Thus, absorption in the He I line serves as an excellent
tracker of the mass outflow leading to mass loss.
Using high resolution spectra from the Fourier Transform
Spectrograph
on the Canada-France-Hawaii telescope (CFHT) and the SOFIN
echelle spectrograph on the Nordic Optical Telescope (NOT), we
analyze
the presence and strength of the He I $\lambda$10830 line
to determine the chromospheric expansion velocity
in 22 luminous cool stars of spectral types G and K. About
half of the stars show absorption at outflowing velocities in excess
of
100 km s$^{-1}$ which are comparable to typical stellar escape
velocities at 1 R_star. For these targets we also explore the
relation
between the extent of He I $\lambda$10830
absorption and X-ray flux. This research was supported by the NSF
REU Program at SAO.
------- Advisor's project abstract:
------- Advisor's project abstract:
The energy injected into the gas by this process has a major effect on
the hot gas. Without it, the gas should have cooled long ago to form
stars, so it probably has a large effect on the process of galaxy
formation. By measuring the energy we can also infer how rapidly the
supermassive black holes grow. We would like to know how often this
happens, how much energy is injected, and whether it happens in all
galaxies. These questions can be answered in part by doing a survey
of nearby galaxies and groups of galaxies from the Chandra archive to
find cavities. From the size of a cavity and the pressure of the
surrounding gas, we can determine the energy required to make it. By
seeing how common they are, we can estimate how frequently they occur
and how much energy they pump into the gas.
------- Advisor's project abstract:
We will complete the visual classification of the remaining
10% of the sample and use this complete survey to study the
global properties of the galaxies in the sample, including
color versus morpological type, color versus luminosity,
the interal extinction in spiral galaxies from color versus
inclination.
If time permits, we will also study differences in galaxy properties
as a function of their environment. The major scientific question
is to understand how the process of galaxy formation depends (or not,
as the case might be) on environment by clearly measuring the
how global properties change versus such parameters as the local
galaxy density and the depth of the potential wells (galaxy clusters)
in which they form.
------- Advisor's project abstract:
and gamma ray sources such as black holes, supernova remnants and
clusters of galaxies; 3) industrial and medical applications where high
resolution x-ray spectroscopy is important to materials and chemical
analysis. The intern will participate in laboratroy experiments
associated with improving the performance of these instruments and
thereby learn low temperature and solid state physics and how to to do
spectroscopic analysis. There are several specific , self-contained
projects that the intern will be able to concentrate on and present to
the group at the completion of his/her internship.
------- Advisor's project abstract:
------- Advisor's project abstract:
The goal of this project is to identify and characterize a sample of
faint asteroids in images from the EXPLORE search for transiting
extrasolar planets. The EXPLORE database consists of thousands of
images of 3 fields taken every 2-3 minutes over a period of 1-2 weeks
per field. The images were taken with CCD mosaic cameras on the CTIO
and KPNO 4m telescopes and the 3.6m CFHT. These observations
constitute a unique dataset in terms of depth and time sampling of the
observations and will therefore lead to a sample of main belt
asteroids fainter than those in most existing studies. Moreover, it
will be possible to produce light curves on the discovered asteroids,
leading to a period measurement for the fastest rotators.
Asteroids can be found in difference images created as a by-product of
the search for transiting planets. Difference images are produced by
subtracting a template image from each frame, thus leaving a mostly
empty frame, with only time-variable and moving objects remaining.
The student will find the asteroids, calculate their orbital elements
(by modifying existing computer programs), produce a luminosity
function for the sample, create light curves, and interpret the
results.
------- Advisor's project abstract:
The focus of the project can be guided by the interests of the
student. We could concentrate on simulations of specific source fields,
on the search for MACHOs, on the study of binarity through
monitoring observations, or on the search for planets.
------- Advisor's project abstract:
We are seeking a motivated student to work with Spitzer imaging data to
attempt to detect elusive nascent galaxies at redshifts of z=4 using a
version of the now well-established dropout technique. The project is
organized into three phases.
The first phase involves collecting and reducing optical broadband data at
the KPNO 4 m Mayall telescope with the MOSAIC wide-field camera. Drs.
Ashby and Huang will be traveling to Kitt Peak to acquire these data (four
nights have already been granted for this purpose, June 9-12), and we
would hope the student would join us for that observing run so as to gain
real hands-on experience with at a world-class astronomical facility (they
have funding to pay your expenses if it fits into your schedule).
The reduction portion of this work would involve standard processing of
the imaging data acquired at KPNO, various quality assessment tasks, and
the generation of a catalog of sources in the resulting combined images.
The second phase of the project will entail `value-added' analysis to
the catalog. Among other things, the catalog would be combined with an
existing catalog of sources detected by IRAC, and searched for objects
that are visible to IRAC but only weakly detected or not detected at all
by the MOSAIC camera. Such optically-faint infrared-bright objects will
form the basis of a sample of candidate high-redshift galaxies.
The third phase will be a check on the validity/feasibility of the
selection technique. Existing spectroscopic redshift databases can be
examined for overlap with the sample, and photometric redshift techniques c
an
also be applied as proof-of-concept.
Completion of the first two phases of the work alone would certainly be
worthy of a AAS poster presentation, and we expect that the student should
be able to accomplish those and possibly most or all of the third portion
in the 9 or 10 weeks available. The first two phases constitute the
primary objective of the student's work. We would hope, however, that the
student would be able to make significant contributions in the third
phase, and woule want to be involved in subsequent proposals that we plan
in order to follow up on the most promising sources spectroscopically.
That portion of the plan would require a large-aperture observatory and
would not of course be possible on the short timescales of the summer work
period. It would nonetheless give the student further scope for work in
this field if he/she were interested in building on the experience.
------- Advisor's project abstract:
Because our original GTO sample was designed to sample as wide a
range of spectral types as possible, with a only a few representatives
for each spectral type bin, we need to expand our sample size of T dwarfs
to better test how observation compares to theoretical modeling for
these objects. An additional sample of T dwarf data has been acquired
under the Nearby Stars GTO program for this purpose.
The student will reduce and analyze IRAC images for about a dozen
relatively nearby brown dwarfs. The student will become familiar with
the IRAC camera and how the data were taken with this space-based
instrument. Software developed locally will be used to produce
cosmic-ray-cleaned, co-added data from multiple exposures of the same
object. Routines in IRAF will be used to extract the photometry for
the objects of interest from each field. These new data will be
combined with existing data for late-M, L, and T dwarfs, to better
investigate the preliminary conclusions we have drawn from the data
analyzed thus far about T dwarfs in the solar neighborhood.
1) Jennifer Blum's project abstract
PROJECT TITLE: Stellar Rotation:
ADVISOR: Dr. Andrea Dupree
INTERN: Jennifer Blum, Colulmbia U.
MENTOR: Jeno Sokoloski
Some old red giant stars in the field of the galaxy
appear to be rotating rapidly. This is puzzling because
as stars evolve and their radius increases, the stars
should rotate less rapidly not more rapidly. Unless,
that is, the star 'swallows a planet' as its radius
increases, and the angular momentum absorbed from the planet
spins up the star. The rotation of a star may also
affect the mass loss of the star, and has been offered
as a possible explanation of the different structure
of the horizontal branch in globular clusters. And a 3rd
area of interest concerns blue stragglers that may
be rotating rapidly producing a spectral signature that mimics
a circumstellar disk. Rotation rates are generally
not available for these stars. One or all of these
areas could become the reu project for the summer.
2) Laura Book's project abstract
PROJECT TITLE: FU Orionis outbursts
ADVISOR: Dr. Lee Hartman
INTERN: Laura Book
MENTOR: Debarati Chattopadhyay
The purpose of this project is to make time dependent calculations
of simple accretion disk models with an aim toward explaining
FU Orionis outbursts. These events consist of jumps in mass
accretion rate by several orders of magnitude in protoplanetary
disks. The large, rapid increases of mass provide significant
physical constraints on the structure of pre-planetary disks that
are otherwise unobtainable. The project will consist of calculating
the evolution of disks with a two-zone model that allows for the
effects of limited disk ionization on the magnetorotational instability
and a parameterized version of angular momentum transport by
gravitational instability. The results of these calculations will be
used to construct light curves to compare with observations.
3) Krzysztof Findeisen's project abstract
PROJECT TITLE: AGN Heating of Galaxies and Groups
ADVISOR: Dr. Paul Nulsen
INTERN: Krzysztof Findeisen
MENTOR: Ryan Hickox
X-ray observations with the Chandra satellite have shown that large
amounts of energy can spew from supermassive black holes, also called
active galactic nuclei (AGN), at the centers of large galaxies. The
energy emerges from AGN in pairs of opposing jets and gets deposited
in the surrouding region. In the massive elliptical galaxies and
groups of galaxies that have atmospheres of hot X-ray emitting gas,
the energy inflates cavities in the gas. The plasma inside the cavity
often emits at radio wavelengths, so we see a 'radio lobe' inside it.
In some cases Chandra has also detected shock fronts (like sonic
booms) that surround the cavities, created when the cavities are
inflated with explosive speed.
4) Conrad Hutchenson's project abstract
PROJECT TITLE: IR Properties of Galaxies in Clusters and Groups
ADVISOR: Dr. John Huchra
INTERN: Conrad Hutchenson
MENTOR: Nathalie Martimbeau
The 2 Micron All-Sky Survey is the source of a major new
catalog of galaxies with well measured photometric properties
in the near infrared. Distances/redshifts have now been measured
for a complete sample of ~24,000 galaxies from this catalog
and morphological types have been estimated for almost
all the galaxies.
5) Harrison Prentice-Mott's project abstract
PROJECT TITLE: Cryogenic X-ray Detector Laboratory
ADVISOR: Dr. Eric Silver
INTERN: Harrison Prentice-Mott
MENTOR: TBD
The student will learn about broad band , high resolution x-ray and
gamma-ray detectors that are being developed for use in space- and
ground-based applications. These include fundamental physics
measurements of highly charged ions produced in heavy ion accelerators
and laboratory plasmas; 2) spectroscopic measurements of cosmic x-ray
6) Michael Rutkowski's project abstract
PROJECT TITLE: The Supernova Remnant E0102-72
ADVISOR: Dr. Eric Schlegel
INTERN: Michael Rutkowski
MENTOR: TBD
E0102-72, a remnant in the Small Magellanic Cloud, has a circular
shape with 'spokes' connecting back to the center. It shows strong
emission lines of oxygen and because of this emission, it has been
used to monitor the increasing absorption layer on the ACIS detector
on Chandra. That means there is a large quantity of data on this
object available in the data archive. This project will extract the
best of the data, those pointings closest to the optical axis of the
telescope, and sum them to (1) search for a point source of emission;
(2) search for time-dependent motion in the rim. The second is
particularly interesting: over approximately 6 years of observations,
the reverese shock has been moving all that time. It may be detectable
in the SE portion of the remnant where a sharp rim exists.
7) Shannon Schmoll's project abstract
PROJECT TITLE: A Search for Asteroids in the EXPLORE Project Dataset
ADVISOR: Dr. Gabriela Mallen-Ornelas
INTERN: Shannon Schmoll
MENTOR: Matt Holman
The currently accepted theory for the formation of planetary systems
postulates that terrestrial planets formed by the collisional growth of
kilometer-sized rocky bodies known as planetesimals. Asteroids are
leftover relics from this phase in the history of the Solar System. It is
believed that the asteroid belt contains objects of different origins,
ranging from planetesimals to fragments of planet embryos. The size
distribution of asteroids is critical for understanding their collisional
history.
8) Megan Schwamb's project abstract
PROJECT TITLE: Applications of Gravitational Lensing: Light Curve Studies
ADVISOR: Dr. Rosanne Di Stefano
INTERN: Megan Schwamb
MENTOR: TBD
One way to detect and study masses lying between us and a
distant bright source field is to study light curves that may
contain evidence of gravitational lensing by these masses.
A new generation of observing programs is being planned.
We will carry out some theoretical studies that can serve as
input to the design of these programs, optimizing their potential
to study dark matter, and also to teach us about local stellar
remnants.
9) Paul Sell's project abstract
PROJECT TITLE:
High-redshift Galaxies Study
ADVISOR: Dr. Matt Ashby
INTERN: Paul Sell
MENTOR: Jia-sheng Huang
The Spitzer Space Telescope is the fourth and final great observatory
and has created entirely new opportunities to study and better understand
objects in the distant, early universe. This is owing to a combination of
its unprecedented sensitivity in the mid-infrared (3-10 microns) and its
privileged position in a novel earth-trailing orbit, where the celestial
backgrounds are very low and even thermal emission from the earth is minimi
zed.
10) Sarah Sonnett's project abstract
PROJECT TITLE:
Spitzer/IRAC Photometry of T Dwarfs
ADVISORs: Dr. Brian Patten and Dr. Massimo Marengo
INTERN: Linda Watson, University of Florida
MENTOR:
The Spitzer Space Telescope is one of NASA's Great Observatories.
One of the three science instruments on board Spitzer is the Infrared
Array Camera (IRAC), a four channel camera that uses two pairs of
256x256 pixel InSb and Si:As IBC detectors to provide simultaneous
images at 3.6, 4.5, 5.8, and 8 microns. With the goal to define the
IRAC colors for brown dwarfs, we have acquired photometry for some
~80 stellar and sub-stellar mass objects with spectral types of late-M,
L and T. Our data shows that the T dwarfs stand out from the other brown
dwarfs in IRAC colors, and provide the most insight into the nature of brown
dwarf atmospheres. In particular, we find that the T dwarf photometry
and colors do not agree entirely with the predictions of theoretical
models, suggesting there is a second parameter, other than temperature,
that one must consider. The most likely candidate is mass, since
sub-stellar mass objects cool continuously after their formation.
Among objects with similar spectral type, the range of mass suggested
by our sample is from about 15 to 70 Jupiter masses.
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