Colloquium Schedule for Fall 2007
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Colloquium Schedule for Fall 2007 |
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3:45-Refreshments in LGRT 1033 Lounge; 4:00-Talk in LGRT 1033 Lecture Area SEPTEMBER 6: SEPTEMBER 13: SEPTEMBER 20: Feedback from massive stars and accreting black holes has proven to be a key ingredient in successful models of galaxy evolution. Yet much about the feedback process is still poorly understood due to a lack of direct observational constraints. To help remedy this, we are studying a population of massive post-starburst galaxies at z~0.6. These objects are the likely remnants of major mergers, observed a few hundred million years after the peak of their star formation and AGN activity. In a 70% of our sample we detect Mg II absorption lines which are blueshifted by 500 - 2000 km/s with respect to the stars. We hypothesize that the absorbing material represents a fossil galactic wind launched near the peak of the galaxy's activity. We estimate the mass and energy of the outflow and conclude that feedback from an AGN may have played a role in expelling the cool gas and quenching star formation. We consider the implications of these observations for the formation of early-type galaxies and the pollution of the intergalactic medium. SEPTEMBER 27: Astronomy and Astrophysics is undergoing a revolution and the next decade will witness the completion of massive, wide-area, multicolor imaging and spectroscopic surveys of the local and distant Universe. In fact, the amount of astronomical data being made available is doubling every year. Hubble's Space Telescope Science Institute (STScI) has been responsible for how most of the world views our universe. Given the coming flood of astronomical information, we wished to allow users to actively explore the cosmos themselves, accessing the very data that researchers use. In this talk I will describe the development of STScI's participation in the creation of Sky in Google Earth and demonstrate some of the capabilties we will use as a springboard for discover, education, and, yes, even research. OCTOBER 4: Over 240 exoplanets are known to orbit nearby stars. Now that their existence is firmly established, a new era of ``exoplanet characterization'' has begun. A subset of exoplanets---called transiting planets---pass in front of their stars as seen from Earth. Transiting planets have immeasurably changed the field of exoplanets because their physical properties, including average density and atmospheric thermal emission, can be now be routinely measured. I will summarize the observations and their interpretation of over twenty known hot transiting exoplanets. I will discuss how the race to find habitable exoplanets has accelerated with the realization that small planets around small stars can be both discovered and characterized with current technology. OCTOBER 11: Galaxy evolution studies in clusters at intermediate redshift (z>0.4) have focused on the most massive clusters usually detected in x-rays. However, the descendants of these clusters are so rare as to be nearly absent in local cluster samples. I will present results from a study of intermediate redshift clusters whose velocity dispersions make them the likely progenitors for the bulk of clusters in the local Universe. These clusters are part of the ESO Distant Cluster Survey (EDisCS) which constitutes the largest well studied homogeneous sample of clusters at 0.4<0.8. Specifically, I will discuss the red sequence galaxy luminosity function and its evolution, with an eye towards tracking the assembly history of the red galaxy population in local clusters. I will also present some early results on Spitzer observations of these clusters which aim to characterize the star forming population and its evolution. I will discuss some implications that these observations have for the growth of clusters over half of cosmic time. OCTOBER 18: The abundance of heavy elements in the ISM of star-forming galaxies represents a fundamental metric of the galaxy formation process. This metallicity reflects the gas reprocessed by stars, and the metals returned to the ISM by supernova explosions. Furthermore, galaxies display universal correlations among luminosity, stellar mass, and metallicity. The form and evolution of these correlations as a function of redshift lend insight into the infall and outflow of gas in galaxies as they build up their stellar populations, and provide important constraints on the nature of star-formation "feedback," a crucial ingredient in models of galaxy formation. Here we present evidence, based on rest-frame optical spectroscopy of galaxies at z~1.0-2.5, that the physical conditions in star-forming regions at high redshift are qualitatively different from those in the local universe. These differences have implications for understanding galaxy metallicities and, perhaps more fundamentally, star formation, itself, during an important epoch when the properties of today's galaxy population were still in the process of coming into place. OCTOBER 25: Recent cosmological measurements combined with simulations of the growth of structure now explain an impressive array of astrophysical phenomena on large scales and at high redshift. By contrast, there has been little progress towards understanding galactic structure in the "era of precision cosmology". In this talk I will highlight some key differences between the kinematics of spiral galaxies and predictions from the standard galaxy formation framework, and I'll present a new velocity field model to assess the role of non-circular motions in generating some of these discrepancies. I will also discuss recent results from the ALFALFA HI legacy survey that constrain the abundance of low-mass, HI-rich starless halos in the local volume. NOVEMBER 1: Abstract: A Redshift Search Receiver is presently being completed for use on the LMT in the next year. The primary motivation for building this receiver is the measurement of redshifts of sub-millimeter galaxies, which are believed to be galaxies in their early stages of evolution. Large numbers of these objects are now detectable with continuum cameras, but redshift determinations are essential to understand their properties. While SMG's are quite luminous in the submm to IR, only a small number are detectable in the visible so redshifts can not be measured in the standard way. The RSR will measure redshifts through a very wideband search for CO lines in the 3mm window. This talk will describe the scientific motivation for building the receiver, including the likelihood that we will be able to measure a statistically useful population. I will also describe the results of early observations using the receiver from the FCRAO 14m telescope, which include other scientific goals such as line surveys in nearby galaxies. NOVEMBER 8: In the past two years the number of satellite galaxies around the Milky Way has doubled. These newly discovered objects have luminosities similar to the faintest globular clusters, but kinematics and metallicities which firmly suggest that they are dwarf galaxies. I present Keck/DEIMOS spectroscopy for eight of these ultra-faint satellites. All are highly dark matter-dominated with mass-to-light ratios approaching 1000. These ultra-faint dwarf galaxies substantially alleviate the discrepancy between the observed number of Milky Way satellites and that predicted by standard Lambda Cold Dark Matter models. I will discuss both the astrophysical and cosmological implications of this new galaxy population. NOVEMBER 15: Searching for terrestrial planets will be a (perhaps the) key astronomical program for the next decade and beyond. We know that Earth, the only example we have to hand, has undergone significant evolution over the past 4.5 Gyrs. It is therefore vital that we understand the age distribution of the nearby stars, both to optimise our search strategies and to ensure that we will be able to recognise earth analogues when we find them. I will give a brief outline of one approach to tackling this issue, which, at the same time, allow us to probe the age-metallicity relation of the local Galactic Disk. NOVEMBER 22: NOVEMBER 29: The early evolution of a protoplanetary disk is characterized by active accretion and the ejection of collimated mass outflows. The outflows are almost certainly accretion-powered since there is a robust correlation between mass accretion and outflow rates over many orders of magnitude, although how they are launched remains a mystery. Establishing their origin is critical for determining the angular momentum evolution of star-disk systems, as they may spin down the star during the accretion phase and/or aid in transporting angular momentum in the disk during the era of planet formation. They likely also play a role in disk clearing, pumping energy into molecular clouds, and terminating the infall of material from the cloud to the disk. Probing the wind launch and acceleration region in the inner AU of the accretion disk via high resolution spectroscopy offers a promising means of identifying the origin of these ubiquitous but mysterious outflows. DECEMBER 6: The current state of our understanding of the nature of the baryon content of galaxy groups, derived largely from a large body of X-ray observations, leaves us with two key questions. First, what are the relative fractions of the hot, warm/hot, and neutral gas in galaxy groups, and how is each phase distributed within groups? Second, how has the baryon content of galaxy groups evolved over time and what is its relationship to the dynamical evolution of the group? The results from a number of investigations of the HI content and deep searches for diffuse synchrotron emission in groups are now shedding light on the evolution of the baryon content of galaxy groups. I will review recent results from t DECEMBER 13: |