Astrophysics Science Division Colloquium Series
Schedule: Spring 2010

Astrophysics Science Division Colloquium Series
Schedule: Spring 2010

Through the courtesy of the speakers since 2004, some presentations are available on line.

Recent schedules:

  • 2009, Fall
  • 2008, Spring
  • 2008, Fall
  • 2008, Second Quarter
  • 2008, First Quarter

    ASD Colloquia are Tuesdays at 3:45 pm (Meet the Speaker at 3:30 pm)
    in Bldg 34, Room W150 unless otherwise noted.


    Jan 26 David Latham (Harvard-Smithsonian Center for Astrophysics) - Super-Earths and Life
    Note: Special Location - Bldg 34, Room W120 A/B


    Feb 2
    Feb 9
    Attila Kovacs (University of Minnesota) - The Sub-mm Galaxy Show
    Host: Johannes Staguhn
    Feb 16
    Feb 23


    Mar 2
    Alexander Kashlinsky (NASA Goddard Space Flight Center) - Measuring the (Dark) Flow of Galaxy Clusters from CMB and X-ray Data
    Mar 9
    Antara Basu-Zych (Goddard Space Flight Center) - Exploring the Nature of Ultraviolet Luminous Galaxies
    Mar 16
    Brian Metzger (Princeton University) - Observable Signatures of Compact Object Mergers
    Host: John Cannizzo
    Mar 22
    Alfred Krabbe (Director German Sofia Institute) - Traces of Hidden Monsters in Nuclei of Active Galaxies
    Host: Johannes Staguhn
    Please note the special date - Monday, March 22, 2010.
    Mar 23
    Mar 30
    Phil Hinz (University of Arizona) - It's a Long Way Down: Finding Faint Planets and Disks with the LBT Interferometer


    Apr 6
    No Colloquium
    Apr 13
    Luciano Rezzolla (Albert Einstein Institute, Max-Planck Institute for Gravitational Physics) - Modeling the Dynamics of Compact-object Binaries in General Relativity
    Apr 20
    Aki Roberge (Goddard Space Flight Center) - Gas & Dust in Debris Disks: Clues to the Late Stages of Planet Formation
    Apr 27
    Jamie Holder (University of Delaware) - Ground-based Gamma-ray Astronomy; Recent Results from the VERITAS Observatory
    Host: Liz Hays
    Note special room: W120


    May 4
    Maxim Lyutikov (Purdue University) - Solar Physics of Magnetars
    Host: Demos Kazanas
    May 11
    Bill Atwood (SCIPP/University of California, Santa Cruz) - The Evolution of the Fermi-LAT Reconstruction Analysis
    Host: Julie McEnery
    May 18
    John Cannizzo (GSFC) - The Kepler Light Curve of V344 Lyr: Constraining the Physiscs of Accretion Disks
    Host: John Baker
    Note special room: W305
    May 25
    Ted Bunn (University of Richmond) - Cosmology from Future Cosmic Microwave Background Polarization Measurements
    Host: Gary Hinshaw
    Note special room: W120 A/B


    June 1
    Dan Evans (Massachusetts Institute of Technology) - A New Twist on Black-Hole Spin: The Triggering and Cosmological Impact of Radio-Loud and Radio-Quiet AGN Outflows
    Host: Kim Weaver
    June 8
    June 15
    Argyris Nicolaidis (University of Thessaloniki) - Living In Extra Dimensions
    Host: Demos Kazanas

    Super-Earths and Life

    David Latham

    Harvard-Smithsonian Center for Astrophysics

    Tuesday, January 26, 2010


    Transiting planets are special. The amount of light blocked by the planet as it passes in front of its host star sets the size of the planet (relative to the star). If an orbit can be derived from Doppler spectroscopy of the host star, the light curve also provides the orientation of the orbit, leading to the mass of the planet (again relative to the star). The resulting density for the planet can be used to constrain models for its structure and bulk properties. We are on the verge of using these techniques to characterize super-Earths, planets in the range 1 to 10 Earth masses that may prove to be rocky or water worlds. An exciting example is the recent detection by the ground-based MEarth project of a probable water world orbiting Gliese 1214. Space missions such as Kepler and TESS promise to play key roles in the discovery and characterization of super-Earths.

    Transiting planets also provide remarkable opportunities for spectroscopy of planetary atmospheres: transmission spectra during transit events and thermal emission throughout the orbit, calibrated during secondary eclipse. Spectroscopy of super-Earths will not be easy, but is not out of the question for the James Webb Space Telescope. Our long-range vision is to attack big questions, such as "Does the diversity of planetary environments map onto a diversity of biochemistries, or is there only one chemistry for life?" A giant first step would be to study the diversity of global geochemistries on super-Earths and Earth analogs.


    After four years as an undergraduate in physics and math at MIT, I moved up the Charles river in 1961 to study astronomy at Harvard. In the 1960s I worked to establish a new observing station in Arizona for the Smithsonian Astrophysical Observatory. That led to a project to build the MMT on the summit of Mount Hopkins in the 1970s, a collaboration between SAO and the University of Arizona. Then, after twenty years of building telescopes and instruments, I turned my attention more to using the new facilities. My interests ranged from observational cosmology and galaxy redshift surveys to studies of stars and their companions.

    In 1989 I led a team that published the first candidate extrasolar planet found with the Doppler technique, HD 114762b. This planet violated what was expected based on our own Solar system, so the astronomical community was reluctant to accept it: its orbit was elongated, it was too massive, and it orbited too close to its host star to have formed there. Now we know of more eccentric, closer and more massive planets.

    During the 2000s, exoplanet research became one of the hottest topics in modern astronomy. I have focused my research on searches for transiting planets, both from the ground and from space.

    The Sub-mm Galaxy Show

    Attila Kovacs

    University of Minnesota

    Tuesday, February 9, 2010


    I will discuss recent results, which further our understanding of the evasive submillimeter galaxy (SMG) population. SMGs are some of the most luminous objects found anywhere in the Universe. Studying them can help us discover the history of star-formation, and constrain models of structure formation and galaxy evolution.

    First, I will present the new, largest, deepest, and most reliable 870um deep field survey from the 295-pixel LABOCA at the APEX telescope, with a special emphasis on my principal contribution of deriving number counts. In the second part, I will show new results from a Spitzer study of SMGs, which have been characterized with the help of 350um SHARC-2 data. (SHARC-2 got its 'eyes' from the GSFC in 2002, and it is still one of the best and largest submillimeter cameras today.)


    Measuring the (Dark) Flow of Galaxy Clusters from CMB and X-ray Data

    Alexander Kashlinsky

    NASA Goddard Space Flight Center

    Tuesday, March 2, 2010


    In standard cosmological paradigm, large-scale peculiar velocities arise from gravitational instability due to mass inhomogeneities seeded during inflationary expansion. On sufficiently large scales, > 100 Mpc, this leads to a robust prediction of the amplitude and coherence length of these velocities independently of cosmological parameters or evolution of the Universe. For clusters of galaxies, their peculiar velocities can be measured from the kinematic component of the Sunyaev-Zeldovich (SZ) effect produced by Compton scattering of cosmic microwave background (CMB) photons off the hot intracluster gas. I will discuss results from new measurements of the large scale peculiar flows using a large X-ray cluster catalog and all-sky CMB maps from the WMAP satellite. The results cast doubt that the gravitational instability from the observed mass distribution is the sole - or even dominant - cause of the detected motions. Instead it appears that the flow extends across the observable Universe and may be indicative of the primeval preinflationary structure of space-time and its landscape.


    Exploring the Nature of Ultraviolet Luminous Galaxies

    Antara Basu-Zych

    Goddard Space Flight Center

    Tuesday, March 9, 2010


    Many studies have focused on the nature of high-redshift (z>2) UV-selected galaxies (i.e, Lyman Break Galaxies (LBGs) and Lyman Alpha Emitters (LAEs)) in order to identify what causes their intense star formation and to gain understanding about the formation and evolution of galaxies. However, as distant galaxies, observations of these galaxies require time-consuming, deep coverage in order to sufficiently study their properties. GALEX has identified a population of z<1 galaxies, Ultraviolet Luminous Galaxies (UVLGs)--a subset, the supercompact UVLGs (ScUVLGs), were selected to resemble LBGs in their rest-frame ultraviolet properties. As local LBG-analogs, ScUVLGs present an opportunity for studying details of galaxy formation in the early Universe with very high physical resolution and sensitivity; as unique and extreme star-forming systems in the local universe, ScUVLGs merit detailed study. In this talk, I will discuss diverse properties of these galaxies: 1. their environments, 2. the dynamics and kinematics of their ionized gas, and 3. their star formation histories and dust attenuation properties. These studies suggest that mergers play an important role in triggering the star formation in these galaxies. Our results reinforce the connection to high-z LBGs, and distinguish UVLGs as unique systems in the local universe.


    Observable Signatures of Compact Object Mergers

    Brian Metzger

    Princeton University

    Tuesday, March 16, 2010


    The inspiral and coalescence of tight neutron star (NS) and black hole (BH) binaries are thought to be among the most promising sources for the direct detection of gravitational waves (GWs) with ground-based interferometers such as LIGO and Virgo. Optimizing the benefits of a GW detection will, however, require identifying a coincident electromagnetic (EM) signal. One possible source for EM emission from NS-NS/NS-BH mergers is a short-duration gamma-ray burst (GRB), powered by the accretion of material that remains in a centrifugally-supported torus around the BH following the merger. I will review the observational and theoretical status of the connection between short GRBs and NS-NS/NS-BH mergers, focusing in particular on models for the viscous and thermal evolution of the remnant disk, and on the puzzling discovery that many short GRBs are followed by extended X-ray flaring lasting for roughly 100 seconds after the GRB. This extended emission is difficult to understand within the standard merger paradigm and may require modifying or considering alternative short GRB progenitor models. Another mechanism for producing EM emission from NS-NS/NS-BH mergers is via a supernova-like optical transient powered by the radioactive decay of heavy nuclei synthesized in neutron-rich merger ejecta. I will present the first calculations of the radioactively-powered transients from mergers that include both realistic nuclear physics and radiative transport. I will discuss the prospects for their detection and identification with present and upcoming optical transient surveys via GW follow-up, or even independent of a GW trigger.


    Brian Metzger is currently a NASA Einstein Fellow in the Department of Astrophysical Sciences at Princeton University. He recently completed his Ph.D. in Physics at the University of California, Berkeley under the supervision of Dr. Eliot Quataert. His dissertation, which focused on theoretical models of gamma-ray burst central engines, won the Mary Elizabeth Uhl Prize from the Department of Astronomy at UC Berkeley and the Top Dissertation Prize of the High Energy Astrophysics Division of the American Astronomical Society. Metzger's primary research interests include gamma-ray bursts, supernovae, accretion physics, and magnetohydrodynamical outflows. He is also interested in nuclear astrophysics, including the origin of heavy, neutron-capture elements.

    Traces of Hidden Monsters in Nuclei of Active Galaxies

    Alfred Krabbe

    Director German Sofia Institute

    Monday, March 22, 2010
    (Special Date)




    It's a Long Way Down: Finding Faint Planets and Disks with the LBT Interferometer

    Phil Hinz

    University of Arizona

    Tuesday, March 30, 2010


    The rapid pace of discovery for exoplanets and disks is providing as many surprises as confirmations to our picture of planet formation and system architecture. I will review the state of these observations and describe plans with the LBTInterferometer to further our understanding of exoplanet systems. LBTI will detect warm exozodiacal emission and Jupiter-like planets, and improve our understanding of planetary system formation and evolution. It is also important ground work for the planned detection of rocky, Earth-like planets. Space missions that aim to detect light 7 to 10 decades down need to know first what exists at 3-6 decades fainter than a star.


    I am currently an Associate Professor at the University of Arizona. Much of my effort goes toward building infrared instruments and adaptive optics (AO) systems. The scientific thrust of these developments is the study of other planetary systems. I primarily observe with the MMT, using a secondary-based AO system, and several instruments I built covering the 3-5 micron and 8-25 micron range. In 2001, I began a project to implement an Interferometer for the Large Bincoular Telescope, or LBTI. The instrument will be installed shortly, allowing the fun of observing to begin.

    Modeling the Dynamics of Compact-object Binaries in General Relativity

    Luciano Rezzolla

    Albert Einstein Institute, Max-Planck Institute for Gravitational Physics

    Tuesday, April 13, 2010


    The detection of gravitational waves is eagerly expected as one of the most important scientific discoveries of the next decade. A worldwide effort is now working actively to pursue this goal both at an experimental level, by building ever sensitive detectors, and at a theoretical level, by improving the modeling of the numerous sources of gravitational waves. Much of this theoretical work is made through the solution of the Einstein equations in those nonlinear regimes where no analytic solutions are possible or known. I will review how this is done in practice and highlight the considerable progress made recently in the description of the dynamics of binary systems of black holes and neutron stars. I will also discuss how the study of these systems provides information well beyond that contained in the gravitational waveforms and opens very exciting windows on the physics of black holes and on the relativistic astrophysics of GRBs.


    Gas & Dust in Debris Disks: Clues to the Late Stages of Planet Formation

    Aki Roberge

    Goddard Space Flight Center

    Tuesday, April 20, 2010


    The basic character of debris disks was established soon after their discovery in the mid-80's. These disks around nearby main sequence stars are composed of material (mostly dust) produced by collisions and/or evaporation of extrasolar asteroids and comets. However, fundamental observational questions about debris disks remain unanswered. How much material do debris disks typically contain and how does it evolve with time? What is the composition of their gas and dust? Are planets present or forming in the disks? Answers to these questions will provide insights into the late-stages of planetary system formation and the origins of terrestrial planet atmospheres.

    In this talk, I will explain our current understanding of the place of debris disks in the planet formation process. Progress toward addressing the questions given above will be discussed, with emphasis on recent and upcoming studies of the small but important gas component. Finally, I will outline the implications of debris dust for future efforts to directly image and characterize extrasolar terrestrial planets.


    Ground-based Gamma-ray Astronomy; Recent Results from the VERITAS Observatory

    Jamie Holder

    University of Delaware

    Tuesday, April 27, 2010


    VERITAS is an array of four imaging atmospheric Cherenkov telescopes located near Tucson, Arizona. The array has been operating since 2007 and, following a recent upgrade, is currently the most sensitive gamma-ray observatory in the world in the energy range above ~100 GeV. I will summarize the current status of VERITAS and provide an overview of some of the key results. Fermi-LAT is now providing critical information for TeV target selection, and the interpretation of many results relies on overlapping observations with the LAT and the TeV observatories. I will present some examples, along with possible plans for the future.


    Jamie Holder received his doctoral degree in gamma-ray astronomy from Durham University. Since that time, he has participated in several ground-based gamma-ray telescope projects (CANGAROO, CELESTE, and Whipple/VERITAS). Jamie is now on the faculty at the University of Delaware in the department of Physics and Astronomy and the Bartol Research Institute. His research focuses observations with VERITAS, which is currently the most sensitive telescope at energies above 100 GeV.

    Solar Physics of Magnetars

    Maxim Lyutikov

    Purdue University

    Tuesday, May 4, 2010


    Magnetars, a special class of about a dozen neutron stars, poses, perhaps, the highest magnetic fields in the Universe, exceeding the quantum magnetic field. The evolution of magnetars and their high energy activity parallels, in some respects, that of the Solar flares, from the production of magnetic field in a turbulent dynamo in the interior of the star to generation of bright X-ray flares and powerful ejections. There are important differences between Solar and magnetar activities: magnetars have a solid crust, their flares and persistent emission occur in highly relativistic regime, radiative processes are strongly affected by magnetic field.


    The Evolution of the Fermi-LAT Reconstruction Analysis

    Bill Atwood

    SCIPP/University of California, Santa Cruz

    Tuesday, May 11, 2010


    An adage among backpackers is "...if you care about the ounces, the pounds will take care of themselves!" The details matter. All the pieces of the LAT design existed pre 1992 in large measure due to the spate of detector R&D done in anticipation of the Super Conducting Super Collider. At the conceptual level, repackaging them for a space mission was the "easy" part. The subsequent detailed studies to optimize the design and the reconstruction analysis however are at the heart of the success of the LAT and continue to evolve today. This talk will detail many of these small but incrementally important developments with an eye to provide guidance for similar efforts in the future.


    The Kepler Light Curve of V344 Lyr: Constraining the Physiscs of Accretion Disks

    John Cannizzo


    Tuesday, May 18, 2010


    Kepler is providing a wealth of information on stellar variability, aside from searching for Earth-like planets. The short orbital period cataclysmic variable V344 Lyr is one of a handful of dwarf novae in the observing field of Kepler. A light curve of ~200 d has been accumulated at 1 minute cadence which far surpasses in quality that generally available for long term light curves of dwarf novae. The data cover two superoutbursts and about 10 regular outbursts. I will discuss detailed time dependent modeling of the physics of accretion disks, and the constraints imposed by these high fidelity data.


    Cosmology from Future Cosmic Microwave Background Polarization Measurements

    Ted Bunn

    University of Richmond

    Tuesday, May 25, 2010


    Cosmic microwave background (CMB) anisotropy observations such as those of WMAP are among the leading sources of evidence in support of the cosmological "standard model." Observations of the linear polarization of the CMB have the potential to provide stringent tests of this paradigm and may even provide a measurement of the energy scale of inflation. CMB polarization maps can be expressed as a sum of a scalar (E) and a pseudoscalar (B) component. The inflation signature is predicted to reside in the B component, which is much weaker than the E component. I will review the physics of CMB polarization, emphasizing the geometrical nature of the E/B decomposition. Contamination of the B component from the E component, or worse yet from the unpolarized emission, is a significant concern in the design of B mode experiments. I will discuss strategies for mitigating this leakage in future experiments. For instance, interferometers are subject to different, and arguably less severe, sources of leakage than imaging telescopes.

    As a side benefit, CMB polarization measurements may shed light on some of the large-angle "anomalies" that have been claimed to be detected in WMAP. The statistical analysis of these anomalies is highly controversial, and a (largely) independent data set covering the same physical scales is needed to resolve the controversy. CMB polarization should provide such a data set.


    A New Twist on Black-Hole Spin: The Triggering and Cosmological Impact of Radio-Loud and Radio-Quiet AGN Outflows

    Dan Evans

    Massachusetts Institute of Technology

    Tuesday, June 1, 2010


    Outflows in AGN may be the key mediator for regulating star formation as galaxies evolve from blue, high accretion-rate, spirals to old, 'red and dead' ellipticals. But how do outflows occur in the first place? What are the key differences between relativistic outflows (jets) and non-relativistic outflows (winds)? Moreover, can we understand what physical conditions near a black hole produce them in the first place? I will present a series of new observational, computational, and theoretical advances that shed light on these key questions. I will show that both relativistic and non-relativistic outflows have key implications for feedback and galaxy evolution, and demonstrate how we will soon be able to use observations of AGN to infer the cosmological evolution of extragalactic jets as a function of black-hole spin.


    Living in Extra Dimensions

    Argyris Nicolaidis

    University of Thessaloniki

    Tuesday, June 15, 2010


    In models unifying gravity and the other forces, gravity propagates, besides the usual four dimensions, into additional extra dimensions and gravity becomes strong at TeV energies. We look for signatures of extra dimensions and strong gravitational phenomena in i) cosmic rays, attributing the cosmic ray knee to produced gravitons, escaping in the extra dimensions ii) LHC, with the production of microscopic black holes iii) unconventional neutrino oscillations, where a flavor neutrino mixes with a singlet neutrino living in the bulk iv) photon mixing with an axion living in extra dimensions, providing new explanations for the transparency of the universe to high energy photons and for the dispersion of time arrival of the MAGIC photons.


    Elizabeth Hays
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