Research
For four months of the 2005-2006 year, I was an Research Experience for
Undergraduates (REU) student researcher at the Cerro-Tololo Inter-American
Observatory, in Chile. I worked on longterm monitoring of NGC 2141 as part of
the WIYN Open Cluster Study with Dr. Stella Kafka.
I've worked previously with Dr. Donald Hoard (Pomona College) on mining the
Two Micron All Sky Survey (2MASS) and Spitzer Space Telescope data for binary
systems containing infrared white dwarfs and then finding optical
counterparts. The primary goal of the program is to study the group
properties of infrared samples of white dwarfs, but we are also finding a
serendipitous set of objects with previously unknown, low mass companions.
I've observed at Palomar Observatory as part of this project, and also spent a
week working with the GoldCam spectrometer on the 2.1-meter telescope at Kitt
Peak National Observatory.
I have searched the Sloan Digital Sky Survey (SDSS) for transient and variable
objects, including asteroids, variable stars, supernovae, gamma-ray burst
afterglows, and quasars, to characterize their properties on various
timescales. This work was done in collaboration with Dr. Masao Sako, of
Stanford University, and resulted in a SLAC publication on the overall
variability of the sky background.
In my sophomore year, I completed an REU project in the molecular physics lab
of Dr. Tom Slanger and Dr. Dave Huestis (of SRI International), calculating
orbital distributions of molecular spectra. We applied our results to study
nightglow in the Earth's upper atmosphere via several forbidden transitions
of O2.
I began my graduate studies in Fall 2006, and am working with Dr. Chris Churchill
in the Extragalactic research group. I am currently interested in large-scale
optical surveys in the time domain, the phenomenology of gamma-ray burst
afterglows, and interstellar materials, to name but a few topics.
My current project involves studying the dynamics of gas within the Milky Way,
to better understand its evolution. Key components include a hot corona,
built of highly ionized, diffuse layers of gas, tidal streams of material
stripped from the Magellanic Cloud satellite galaxies, and high velocity
clouds, possible remnants of galactic formation. The combination forms a
complex system, covering a wide range of ionization states and densities.
How can we observe and study this gas? There are a hundred sight-lines to
ultra-luminous deep space quasars distributed across the sky, and their
spectra are uniquely suited to illuminate the distribution of gas within the
Milky Way halo. As chemical ions within the gas absorb light emitted from the
distant quasars, they leave a characteristic pattern of absorption features at
key wavelengths within the quasar spectra.
With Dr. Churchill and theorist Dr. Anatoly Klypin, I plan to study the
formation and evolution of galaxies like the Milky Way in a CDM universe. We
will utilize high-resolution cosmological simulations to resolve structure on
sub-kiloparsec scales, critical to determining the formation of galactic
disks. The physical processes implemented in the code include radiative
cooling, star formation, metal enrichment and thermal feedback due to type II
and type Ia supernovae.
We will replicate observational data sets with these theoretical simulations
of the Milky Way. We can then trace quasar sight lines through the modeled
Milky Way disk in all directions, generating model spectra to compare
statistically to quantitative results from the Hubble Space Telescope Quasar
Absorption Line (QAL) Key Project (Savage 1993, AJ, 413, 116) and Goddard High
Resolution Spectrograph observations (Savage 1997, AJ, 113, 6). We should
thus be able to directly compare the covering factors, scale heights, and
kinematic, chemical, and ionization conditions of Civ, Nv, and
Ovi, and the redistributions of these metals in the halo of the Milky
Way to observationally measured quantities. We will also constrain the
underlying temperatures, density, and ionization structure of gas in the halo.
I am pleased to acknowledge support from a Consortium for Higher Education
HED Fellowship for women in the sciences. This research is supported by a grant from the New Mexico Space Grant Consortium (NMSGC).
Publications
Cool Companions to White Dwarf Stars from the Two Micron All Sky Survey All Sky Data Release,
Hoard, D. W.; Wachter, S.; Sturch, Laura K.; Widhalm, Allison M.; Weiler, Kevin P.; Pretorius, Magaretha L.; Wellhouse, Joseph W.; Gibiansky, Maxsim; Astronomical Journal, 2007
WIYN Open Cluster Study: Long Period Variables in NGC 2141,
A. Widhalm & S. Kafka 2006
A Search for Variable Sources in the Sloan Digital Sky Survey,
A. Widhalm & M. Sako 2004, SLAC-TN-04-072, September 2004
Nightglow Vibrational Distributions in the
A3Σ+u and A'3Δ
u States of O2 Derived from Astronomical Sky
Spectra,
T. G. Slanger, P. C. Cosby, D. L. Huestis, & A. M. Widhalm 2004, Annales
Geophysicae, 22, 3305
Meetings
January 2008: American Astronomical Society meeting:
January 2007: American Astronomical Society meeting:
- WIYN Open Cluster Study Long-term Monitoring: NGC 2141
A. M. Widhalm & S. Kafka
- Evidence for Evolution in Weak MgII Absorbers at z < 1.5
J. Evans, C. W. Churchill, M. I. Murphy, & A. M. Widhalm
- Spatial Probing of MgII Absorption in ``Halo'' Gas through Adaptive Mesh Refinement Simulations of Galaxies
C. W. Churchill, G. Kacprzak, D. Ceverino-Rodriguez, J. Evans, & A. Widhalm
- Cool Companions of White Dwarfs from 2MASS
D W. Hoard, S. Wachter, L. K. Sturch, A. M. Widhalm, K. P. Weiler, J. W. Wellhouse,
& M. Gibiansky
December 2003: American Geophysical Union meeting, Vibrational Distributions in the A3Σ+u and A'3Δ u
States of O2 in the MLT Nightglow: Results from Astronomical Sky
Spectra
A. M. Widhalm, T. G. Slanger, P. C. Cosby, & D. L. Huestis
Future Work
I obtained my M.S. degree in August of 2008, and have accepted a position with the
Gemini Observatory in Chile, working to improve the quality of the telescope data
products.
