Spring 2005 Astronomy Colloquia - The University of Texas at Austin

January 25, 2005

Rob Kennicutt
University of Arizona
\Nearby Galaxies as Revealed by the Spitzer SINGS Legacy Project
The Spitzer Infrared Nearby Galaxies Survey is a comprehensive multi-wavelength imaging
and spectroscopic survey of 75 nearby galaxies. It is designed to provide definitive information
on the large-scale star formation processes in galaxies and on the interaction of young stars
with the surrounding interstellar medium. The early results from SINGS reveal the enormous
diversity of infrared morphologies and spectral energy distributions (SEDs) along the Hubble
sequence and as functions of galaxy mass and metallicity. Our current analyses are focused
on detailed comparisons of UV, visible, infrared, and radio star formation rate indicators
within individual galaxies, quantifying the differences in infrared SEDs and extinction properties
within and between galaxies, and compiling a base set of reference image and spectral libraries
for cosmological applications.

February 1, 2005

Lynn Jones Eaton
University of Texas
Active Learning Techniques
"Active Learning" is, in short, anything that students do in a classroom other than
merely passively listening to an instructor's lecture. Active learning techniques enhance
lectures and actively engage students in the learning process. Techniques will be shared and

February 8, 2005

Frederick Chang
University of Texas
Information Security: What You Need to Know Today
Unfortunately, viruses, worms, spyware, denial of service attacks and computer network
compromises, in general, have become a way of life. As a result the industry has produced a
blizzard of software and hardware tools to help protect our computers and networks from
malicious attackers.  Is the problem getting any better?  This talk will provide some perspectives
on the problem and challenges facing end-users today and will offer some practical recommendations.
Additionally, the talk will introduce UT’s new Center for Information Assurance and Security
and briefly describe its mission and objectives.

February 15, 2005

Michael Gaffey
University of North Dakota
Mineralogical and Compostional Characterizations of Asteroids: Why? How? What?
Asteroids represent the surviving remnants of the planetesimal population which once filled

the inner solar system and from which the terrestrial planets were accreted. Most of the chemical
and geological evolution of the asteroid parent bodies occured within the first ten million years of

solar system history. The properties of the planetesimals established the initial thermal properties

of terrestial proto-planets Asteroids and their meteorite samples have recorded the chemical

environment of the solar nebula, the early evolution of the Sun, and the collisional environment

in the inner solar system. Sophisticated compositional and mineralogical characterizations of asteroids
provide the basis for revealing these diverse perspectives on solar system history. Our research group
has focused significant efforts on the development of observing protocols and data reduction procedures
to optimize the quality of asteroid spectral data obtained with low-resolution near-infrared spectrographs.
Such data is currently leading to significant improvements in our understanding of the formation epoch
and the early solar system, of the relationships between asteroids and meteorites, and of the impact hazard
by near-Earth objects.

February 22, 2005

Andrew Blain
California Institute of Technology

The Nature and Environments of Ultraluminous High-Redshift Galaxies
Ground-based submillimeter-wave surveys have detected a significant population of very luminous

distant galaxies. I will describe the search to uncover their properties, and their contribution to the
complete picture of galaxy formation. In particular, I will describe the first steps to probing their spatial

distribution, and the pospects for understanding the processes that lead to their very high luminosities,

possibly biased into specific regions, and the prospects for using Spitzer and future facilities to study them
in detail and compile larger samples.

March 1, 2005

Rosie Wyse
Johns Hopkins University

The Stellar Initial Mass Function Long Ago and Far Away
The Stellar IMF at high redshift is of great importance for a wide range of astrophysical problems.

There are two complimentary approaches to the determination of the IMF long ago and far away:
one is to observe directly high redshift objects, and attempt inferences on the stellar IMF from the
integrated spectrum and photometry, while the second approach analyses the fossil record in old stars
at low redshift. The characterization of the stellar IMF in external galaxies, compared to that in the
Milky Way, is a crucial step in deciphering the important physical processes that determine the distribution
of stellar masses under a range of different physical conditions. The low mass stellar IMF at the high
redshifts at which these stars formed is directly accessible through star counts, plus a mass-luminosty
relation. The high-mass IMF at these high reshifts is constrained by the chemical signatures
in the low mass stars that were enriched by the supernoave from the high mass stars. I will
discuss both ends of the IMF at high redshift, in an external galaxy. I will also discuss a new survey
for eclipsing low-mass binaries, to calibrate better the mass-luminosity relation.

March 8, 2005

Tsvi Prian
California Institute of Technology

Gamma-ray Bursts: An Enigma and a Tool

March 22, 2005

Steve Squyres
Cornell University
Science Results from the Mars Exploration Rover Mission

March 29, 2005

Andrea Ghez

Unveiling a Supermassive Black Hole at the Center of our Galaxy
The proximity of our Galaxy's center presents an opportunity to build a case for a supermassive black

hole and to study the black hole's environment and its effects thereon with much higher spatial resolution
than can be brought to bear on any other galaxy. After almost a decade of astrometry from diffraction-
limited speckle imaging at the W.M. Keck 10m telescope, we have moved the case for a supermassive
black hole at the galactic center from a possibility to a certainty; this is based on our recent ability to
determine the orbits of individual stars, which confines the central dark mass of 3.7 million times the mass
of the sun to within 45 AU (1 AU = the Earth-Sun distance), or equivalently, 600 Schwartzschild radii.
With the advent of adaptive optics, which have significantly expanded out studies of the Galaxy's central
black hole through the addition of diffraction-limited spectroscopy and deep imaging at wavelengths
other than 2.2 microns. Spectroscopy has revealed that the stars orbiting in such close proximity are
apparently massive and young; the origin of the stars is difficut to explain, given the strong tidal forces,
and may provide key insight into the growth of the central black hole. Thermal infrared imaging (3.8
microns) has led to the direct detection of plasma associated with the black hole. This source is variable
on timescales as short as 40 min, implying that the emission arises quite close to the black hole, within
5 AU, or 80 Schwartzschild radii. This provides a new, constantly accessible window into the physical
conditions of the plasma in close proximity to the central black hole.

April 22, 2005

Roy Schwitters
UT Austin, Physics

Maya Muon Tomography Project
Plans to explore the ruin of a Maya pyramid in Belize using cosmic ray muon tomography will be

described. Muon tomography was pioneered by Luis Alvarez in the 1960's to explore the Second
Pyramid of Chefren in Egypt. Improvements in detector technology since the Alvarez experiment
suggest that muon tomography may be a practical method for exploring and monitoring relatively large
underground volumes when exposure times of order months are acceptable.

April 26, 2005

Roger Davies
Oxford University

Galaxy Evolution Through the Eyes of SAURON
The SAURON integral field spectrograph on the William Herschel Telescope has completed a survey

of a representative sample of early-type galaxies over a range of luminosity, environment and Hubble
type. I will present results on their stellar kinematics, make dynamical estimates of mass-to-light ratio,
report on the distribution & kinematics of the ionized gas, and characterize the stellar population in terms
of age, metallicity and mass-to-light ratio. I will discuss the implications of these results for dark matter in
in galaxies, their star formation and assembly history.

May 3, 2005

Eiichiro Komatsu and Dan Jaffe
University of Texas

The Cosmic Inflation Probe Study
We will discuss a concept for the Cosmic Inflation Probe (CIP)-a proposed space experiment

with significant UT participation. The development of the concept of Inflation two decades ago was a
critical event in the history of Big Bang cosmology. Inflation essentially saves the Big Bang
by resolving the most important problems: the flatness problem, the smoothness problem, and the growth
of structure. Inflation is what powers the Big Bang but yet we know very little about it: there are hundreds
of inflation models that fit within the current observational constraints. The Universe in the
matter-dominated era does, however, contain echoes of the inflation epoch which encode sufficient
information about the inflaton potential to provide a much more detailed picture of inflation physics.
CIP will precisely measure the power spectrum of the matter distribution at z=3-6.5 across
a large range of spatial scales to produce the best observational constraints on the expansion
history of the universe during inflation, thereby narrowing in on the underlying physics.
We will describe the physical basis for our experiment, the instrument design, and the mission plan.

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