From CASS
Seminars
The CASS Astrophysics Seminar features world-class astrophysicists from around the world speaking on current topics of research. Presentations are aimed at the graduate and post-graduate level, but are open to the general public. CASS seminars take place on Wednesdays from 4:00 - 5:00 p.m. in 280 SERF, unless otherwise noted. The organizers are Prof. Adam Burgasser and Dr. Alexei Kritsuk.
Upcoming Seminars
Winter 2012
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| Speaker
| Title
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| 2/22/2012
| Simon Glover
Postdoctoral Research Fellow
Institut fur Theoretische Astrophysik
| "Molecule formation in the turbulent ISM: Insights from numerical models"
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| Abstract
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| Within the past few years, it has become possible to perform high-resolution three-dimensional simulations of molecular cloud formation and evolution that trace the thermal and chemical history of the gas in addition to its dynamical history. In this talk, I will discuss some of the insights that these simulations provide into the behaviour of real molecular clouds. In particular, I will discuss what we can learn about the physical processes responsible for determining the so-called "X-factor", the conversion factor relating the CO luminosity of a Galactic giant molecular cloud (GMC) to its H2 mass. I will also present some results from recent work exploring the role that molecular cooling plays in determining the star formation rate within GMCs.
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| Date
| Speaker
| Title
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| 2/29/2012
| Jessica Lu
NSF Postdoctoral Fellow
U. Hawaii
| "Star Formation in the Extreme Environments of the Massive Clusters and Supermassive Black Holes"
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| Abstract
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| The formation of stars is a fundamental astrophysical process; and yet we still debate whether it varies with environment. Milky Way young star clusters range in mass over four orders of magnitude; but, the best-studied star forming regions, such as Taurus and Orion, represent only a small range of initial conditions at the low mass end. Young star clusters with masses greater than 10,000 solar masses are promising targets for determining whether the initial mass function (IMF) that results from the star formation process is universal or depends on environment. Such clusters are challenging observational targets as they require high spatial resolution at infrared wavelengths and are heavily contaminated by field stars. I present results from a Keck adaptive optics and HST study of several massive young star clusters in the Milky Way, including around the supermassive black hole at the Galactic Center. Precise IMFs are constructed by using high-precision astrometry and spectroscopy to distinguish individual cluster stars. I will discuss whether the measured IMFs differ for massive clusters at a range of Galactocentric radii and how they compare to the "universal" IMF established locally.
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| Date
| Speaker
| Title
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| 3/7/2012
| Vardha Bennert
Asst. Professor
CalPoly San Luis Obispo
| "The Black-Hole Mass Scaling Relations of Active Galaxies: From the Local Universe out to a Lookback Time of 10 Gyrs"
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| Abstract
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| Supermassive Black Holes (BHs) seem to be ubiquitous in the center of spheroids - elliptical galaxies and bulges of spirals. The tight empirical relations between the mass of the BH and the properties of the host-galaxy spheroid (stellar velocity dispersion sigma, luminosity L, and stellar mass M) discovered in the local Universe indicate a close connection between the growth of BHs and the formation and evolution of galaxies. To understand the origin of these scaling relations, I will present results from a unique three-fold approach. (i) From a sample of ~100 Active Galactic Nuclei (AGNs) in the local Universe, we build a robust baseline of the BH mass scaling relations (MBH-sigma, MBH-L, MBH-M), combining spatially-resolved Keck spectroscopy with SDSS imaging. (ii) We study the evolution of the MBH-sigma and MBH-L relations out to a look-back time of 4-6 Gyrs using Keck spectra and HST images. Our results indicate that black hole growth precedes bulge assembly. (iii) We extend this study out to the pivotal cosmic time between the peak of AGN activity and the establishment of the present-day Hubble sequence, a look-back time of 8-10 Gyrs. We measure spheroid stellar masses using deep multi-color HST images and determine the MBH-M relation. Combining results from (i-iii) allows us to test the hypothesis that evolution is driven by disks being transformed into bulges.
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| Date
| Speaker
| Title
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| 3/14/2012
| Dave Tsang
Sherman Fairchild Fellow
Caltech
| "Resonant Shattering of Neutron Star Crusts"
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| Special Astro Seminar: Friday 12-1pm in SERF 280
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| Speaker
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| 3/16/2012
| Katrien Kolenberg
Postdoctoral Researcher
Harvard-Smithsonian CfA & KU Leuven, Belgium
| "Kepler and the RR Lyrae stars"
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| Abstract
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| The spectacular data delivered by NASA's Kepler mission not only boost the discoveries of planets orbiting other stars, but they also open a window on the inner workings of the stars themselves. Kepler has been a breakthrough for the study of RR Lyrae stars and the still mysterious Blazhko effect. I will present some of the most interesting results obtained so far.
To date, over 40 RR Lyrae stars have been found in the Kepler field. The outstandingly high-precision data of these stars are investigated within the RR Lyrae working group as part of the Kepler Asteroseismic Science Consortium (KASC).
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| Title
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| 3/21/2012
| Andrey Kravtsov
Assoc. Professor of Physics
U. Chicago
| "The chemistry of galaxy formation"
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| Abstract
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| I will present a novel model of star formation based on non-equilibrium treatment ofmolecular hydrogen in self-consistent cosmological simulations of galaxy formation, including effects of self-shielding and shielding by dust. The model predicts strong dependence of the global Kennicutt-Schmidt star formation relation on the metallicity ofthe interstellar medium of galaxies (and a weaker dependence on the interstellar UV field) and can explain recent results indicating inefficient star formation in high-redshift Damped Lyman alpha galaxies at z~3. General considerations and some preliminary simulation results indicate that low efficiency of star formation at high redshifts can have significant implications for galaxy formation and may help resolve many of the main problems and puzzles of galaxy formation within hierarchical CDM scenario. I will also briefly review the current status and challenges facing galaxy formation simulations. I will argue that recent modeling results indicate that correct modeling of galaxy formation requires the right "chemistry" - a non-trivial mix of nonlinear processes - to be treated correctly.
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