List of Past Astronomy Colloquia : 01-Sep-2010 to 31-Dec-2010


Date:   Wednesday 08-Sep-2010
Speaker:   Dr. Philip Hopkins (University of California, Berkeley)
Title:  How do Massive Black Holes Get their Gas (and Get Rid of It)?

Recent observations of tight correlations between supermassive black hole masses and the properties of their host galaxies demonstrate that black holes and bulges are co- eval, and have motivated theoretical models in which feedback from AGN activity regulates the black hole and host galaxy evolution. I’ll review the state of models and observations regarding quasar and AGN fueling and feedback, using new multi-scale simulations that can probe from galaxy scales down to the accretion disk. Combining simulations, analytic models, and recent observations, answers to a number of questions are starting to take shape: How to AGN get triggered? How long do they live? Are there relics in the local Universe -- perhaps even in M31 and the Milky Way -- that provide unique information on the epoch of black hole growth? Is feedback necessary/suf?cient to regulate BH growth? What effects does that feedback have on the host galaxy? And how does this interact with the dynamics of stellar evolution and other sources of feedback in the ISM?


Date:   Wednesday 15-Sep-2010
Speaker:   Dr. Erick Young (USRA)
Title:  SOFIA - First Light and Preparations for Initial Science Flights

SOFIA, the Stratospheric Observatory for Infrared Astronomy, is a specially modified Boeing 747SP aircraft with a 2.7-m telescope. Flying above more than 99% of the water vapor in the Earth's atmosphere, SOFIA will enable observations at large regions of the infrared and submillimeter that are opaque to terrestrial observatories. A joint project of NASA and DLR (the German Aerospace Center), SOFIA has recently completed a series of major flight tests that have fully cleared the operational envelope. I will report on the results of the first light and telescope characterization flight and the efforts leading to the Initial Science Flights this year.


Date:   Wednesday 22-Sep-2010
Speaker:   Dr. Tommy Grav (JHU)
Title:  Observing the Solar System with WISE

In early January, 2010, the Wide-field Infrared Survey Explorer (WISE) began imaging the entire sky with sensitivities in the mid-IR hundreds of times greater than previous surveys. WISE consists of a 40 cm cryogenically-cooled telescope taking simultaneous images at 3.4, 4.6, 12 and 22 microns. WISE recently completed its first full survey of the sky and has exhausted its cryogen. Although WISE itself is an astrophysics mission, NASA’s Planetary Science Mission Directorate has funded an enhancement to the WISE project, called “NEOWISE”, that is dedicated to serving the individual exposures and extracted source lists, providing an interface for small bodies based on orbital elements, and discovering new moving objects. The WISE bandpasses sample the flux from most inner-Solar System bodies near the peak of their thermal emission, making the survey extremely efficient at detecting and discovering solar system objects. Infrared observations are sensitive to the low albedo objects that are preferentially missed by optical surveys. At this time NEOWISE has observed 438 Near-Earth Objects (NEOs), ~150,000 Main Belt Asteroids, ~100 comets, and ~1500 Trojan asteroids. The NEOWISE dataset represents a treasure trove of new information on small bodies in our Solar System that will leave a legacy for decades to come.


Date:   Wednesday 29-Sep-2010
Speaker:   Dr. Joan Centrella
Title:  Black Hole Mergers, Gravitational Waves, and Multi-Messenger Astronomy

The final merger of two black holes is expected to be the strongest source of gravitational waves for both ground-based detectors such as LIGO and VIRGO, as well as the space-based LISA. Since the merger takes place in the regime of strong dynamical gravity, computing the resulting gravitational waveforms requires solving the full Einstein equations of general relativity on a computer. Although numerical codes designed to simulate black hole mergers were plagued for many years by a host of instabilities, recent breakthroughs have conquered these problems and opened up this field dramatically.

This talk will focus on the resulting gold rush of new results that is revealing the dynamics and waveforms of binary black hole mergers, and their applications in gravitational wave detection, astrophysics, and testing general relativity.


Date:   Wednesday 06-Oct-2010
Speaker:   Dr. Jayant Narlikar (IUCAA)
Title:  A SEARCH FOR VERY OLD STARS

This talk will describe a joint work by Vijay Mohan, Nando Patat, Ken Freeman and the speaker to look for stars around 20 Gyr old. The cosmological significance of such a search will be described first, including an alternative cosmology which allows arbitrarily old stars to exist. The search for old stars is carried out in the LMC and colour magnitude diagrams of stars are used to estimate their ages. A group of stars possibly lying close to a subgiant branch of the CMD is identified as likely old stars. Alternative explanations of this group in terms of younger systems are discussed and seen to be rather contrived. Future tests are proposed to decide between these alternatives.


Date:   Wednesday 13-Oct-2010
Speaker:   Dr. Alicia Soderberg (Harvard)
Title:  "A Panchromatic Approach to the GRB-SN Connection"

Throughout history, observational supernova studies have focused almost exclusively on their strong optical emission powered by the radioactive decay of Nickel-56. Yet many of the leading breakthroughs in our understanding of supernovae and their progenitors have been enabled by observations at other wavelengths. For example, through the combination of radio, optical, X-ray and gamma-ray observations, we now know that less than 0 .1 percent of all core-collapse supernovae require "central engines" (compact accreting sources) to power associated gamma-ray bursts. As I will discuss, it is the growing sample of radio and X-ray observations of nearby supernovae that are enabling rapid progress in revealing the nature of the GRB-SN connection. The fundamental question at this stage is clearly: which key progenitor property enables such a small fraction of massive star explosions to give rise to relativistic ejecta, and in turn, GRBs? While progenitor mass, metallicity, and binarity are among the most popular explanations, I will discuss how panchromatic observations (radio, optical, X-ray, gamma-rays) of supernovae and their environments shed light on this puzzle, using our extensive analysis on SN 2009bb as a primary example. I will also present some exciting new results on the optical luminosity distribution for SNe Ibc.


Date:   Wednesday 20-Oct-2010
Speaker:   Dr. Joss Bland-Hawthorn (U. Sydney)
Title:  The HERMES project – reconstructing the ancient Galaxy

The first building blocks of our Galaxy were likely to have been laid down in the first 300 million years after the Big Bang. The first stars that came into being in those early structures have long since disappeared but they may have left behind unique chemical signatures in today's stellar populations. Over the next 13 billion years, the Galaxy grew through a series of mergers and acquisitions into the corporate giant that surrounds us today – 100 billion stars and counting. This was undoubtedly a very complex process that we are far from understanding even with the most sophisticated computer simulations. All stars show evidence of chemical signatures that say something about their past. In this talk, I will describe the basic motivation of the HERMES survey which will attempt to reconstruct the early Galaxy history through the technique of chemical tagging. The HERMES instrument is a major new $10M facility at the AAT that will see first light in 2012.

FURTHER READING:

Freeman K and Bland-Hawthorn J (2002) ARAA, 40, 487 http://adsabs.harvard.edu/abs/2002ARA%26A..40..487F

SHORT BIO:

Joss Bland-Hawthorn is a Federation Fellow at the University of Sydney where he is a Professor of Physics and Associate Director of the Institute of Photonics and Optical Science. Joss is a widely published astrophysicist who has also pioneered many concepts in astronomy and astronomical instrumentation. In 1986, he obtained his PhD in astrophysics from the Royal Greenwich Observatory prior to taking up appointments in Hawaii and Texas. In 1993, he moved to the AAO where he was Head of Instrument Science. In 2001, he proposed the new field of astrophotonics that sits at the interface of astronomy and photonics. In Feb 2009, this field was featured in a Focus Issue of Optics Express featuring remarkable new technologies like OH suppression gratings, laser combs, vortex coronographs, and integrated photonic spectrographs. Joss is a recipient of the 2008 Muhlmann Award for experimental astronomy, and a recipient of the inaugural 2008 Group Achievement Award from the Royal Astronomical Society. This year, he is the Merton College Fellow and the Leverhulme Visiting Professor to Oxford. In 2011, he is the Brittingham Scholar at the University of Wisconsin.


Date:   Wednesday 27-Oct-2010
Speaker:   Dr. Catherine Neish
Title:  Radar Love: Mini-RF Observes the Moon

In June 2009, NASA launched the Lunar Reconnaissance Orbiter (LRO) carrying the Mini-RF synthetic aperture radar (SAR). Since then, Mini-RF has imaged ~50% of the Moon at 30 m resolution, in both polar and non-polar regions. SAR images provide a wealth of information about the surface being imaged, including topography, composition, and centimeter-scale roughness. The unusual radar properties of ice may also lead to its detection in the permanently shadowed regions at the poles of the Moon. In this talk, I will summarize the discoveries made by Mini-RF in its first year of operations. In particular, I will discuss the information obtained by recent radar observations of (a) the LCROSS impact site near the south pole of the Moon, and (b) the optically bright, sinuous albedo features known as lunar swirls.


Date:   Wednesday 03-Nov-2010
Speaker:   Dr. Linda Tacconi (MPE)
Title:  "Gas dynamics, galaxy assembly, and star formation in the early Universe"


Date:   Wednesday 10-Nov-2010
Speaker:   Dr. David Neufeld (JHU)
Title:  Molecular Astrophysics with Herschel

Molecules are ubiquitous in the astrophysical Universe. They have been observed in environments as diverse as interstellar gas clouds, outflows from evolved stars, active galactic nuclei, stellar photospheres, planetary atmospheres, and cometary comae; and they have been observed at distances near and far: in the solar system, in the Milky Way, in nearby galaxies, and in the high-redshift Universe.

To date, more than 150 distinct molecules have been detected in the gas-phase; they range from stable species, such as carbon monoxide and water vapor, to reactive transients. Some molecules were discovered first in interstellar space, and synthesized only subsequently in the laboratory. Molecules are also detectable in the solid phase, in interstellar ices, for example. They are the building blocks for life on Earth, and perhaps elsewhere in the Universe.

Because molecules are important coolants of the astrophysical gas, they play a role in the collapse of interstellar gas clouds to form stars, and of pregalactic clouds to form galaxies. Thanks to their rich spectra of rotational, vibration and electronic transitions, molecules serve as valuable diagnostic probes of the kinematics of - chemical and physical conditions within - the environments where they are found. Thus, observations of molecules, carefully interpreted, have provided unique information of general astrophysical interest, ranging from the temperature of the microwave background, to the masses of black holes in active galaxies. The development of space- based and suborbital platforms for submillimeter, infrared, and ultraviolet astronomy has opened new spectral windows for pursuing molecular astrophysics.

In this talk, I will review what can be learned from the study of astrophysical molecules, and will present recent results obtained using the Herschel Space Observatory.


Date:   Wednesday 17-Nov-2010
Speaker:   Dr. Stephane Courteau (Queen's University)
Title:  "Puzzles in Galaxy Scaling Relations"

Galaxies can be described in terms of their structure, dynamics and stellar populations. Some very robust correlations between various galaxy structural properties, such as total luminosity, maximum circular velocity, and size have been known for more than four decades and yet still lack a theoretical explanation! A fundamental challenge to understanding these scaling relations, and ultimately galaxy formation and evolution, is the (elusive) interplay between visible and dark matter. I will discuss the latest derivations of galaxy scaling relations and our attempts to understand them.


Date:   Wednesday 24-Nov-2010
Speaker:  
Title:  NO COLLOQUIUM


Date:   Wednesday 01-Dec-2010
Speaker:   Dr. J.D. Smith (University of Toledo)
Title:  Dust in Galaxies: Nuisance No Longer

Dust represents less than one-hundredth of one percent of the mass of a typical galaxy, yet is responsible for reprocessing on average one-half of all the luminous energy arising from star formation and accretion within them. I'll review the recent successes and promising future of dust as a tool to study galaxy evolution, including its role as the primary heating agent of the interstellar medium, its unique responses to stellar vs. non-stellar power sources, the potential for using dust as a sensitive tracer of the total gas reservoir, and the ongoing efforts to obtain an accurate census of the dust content and conditions of galaxies in the local universe.


Date:   Wednesday 08-Dec-2010
Speaker:   Dr. Yan Fernandez (U. Central Florida)
Title:  "Ensemble Properties of Icy Small Bodies"

The Spitzer Space Telescope has provided and continues to provide a wealth of photometric data on small bodies of the Solar System.

I will discuss recent results on the thermal and reflective properties of various primitive small bodies of the Solar System -- cometary nuclei, Trojans, and trans-Neptunian objects. These results have been obtained through the combination of Spitzer observations in the mid-IR and ground-based observations in the visible and near-IR. By observing a statistically-significant sample of bodies in each population, we can understand their ensemble properties and thereby learn more about their evolution.


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