April 4, 2007 | 3:30 PM | RI 480 Three-Year Results from WMAP (with Commentary) Gary Hinshaw, NASA Goddard
The data from the first three years of operation of the Wilkinson Microwave Anisotropy Probe (WMAP) satellite provide detailed full-sky maps of the cosmic microwave background temperature anisotropy and new full-sky maps of the polarization. Together, the data provide a wealth of cosmological information, including the age of the universe, the epoch when the first stars formed, and the overall composition of baryonic matter, dark matter, and dark energy. The results also provide constraints on the period of inflationary expansion in the very first moments of time. These and other aspects of the mission results will be discussed and commented on.
WMAP, part of NASA's Explorers program, was launched on June 30, 2001. The WMAP satellite was produced in a partnership between the Goddard Space Flight Center and Princeton University. The WMAP team also includes researchers at the Johns Hopkins University; the Canadian Institute of Theoretical Astrophysics; University of Texas; University of Chicago; Brown University; University of British Columbia; and University of California, Los Angeles.
May 2, 2007 | 3:30 PM | RI 480 Wide-Field Surveys of the Optical Sky: The Large Synoptic Survey Telescope (LSST) Steven M. Kahn, Stanford University
Recent technological advances have now made it possible to carry out deep optical surveys of major fractions of the visible sky. Such surveys enable a diverse array of astronomical investigations, ranging from the search for small moving objects in the solar system to studies of the assembly history of the Milky Way. In terms of cosmology, wide-field surveys can yield tight constraints on models of dark energy using a variety of independent techniques.
The Large Synoptic Survey Telescope (LSST) is the most ambitious project of this kind that has yet been proposed. With an 8.4 m primary mirror, and its 3.2 Gigapixel, 10 square degree camera, LSST will provide a nearly an order of magnitude improvement in survey speed over all existing surveys, or those which are currently in development. Over its ten years of operation, LSST will survey 20,000 square degrees of sky in six optical colors down to 27th magnitude. At least a thousand distinct images will be acquired of every field, enabling a plethora of statistical investigations for intrinsic variability and for control of systematics in deep imaging studies.
I will describe some of the science that will be made possible by the construction of LSST and give a brief overview of the technical design.
May 9, 2007 | 3:30 PM | RI 480 Star Formation at High z: Evidence for two types of DLAs? Arthur M. Wolfe, CASS, University of California, San Diego
Damped Ly_ absorption systems (DLAs) are a population of objects that act as neutral-gas reservoirs for star formation at high redshift. If the star formation efficiency in DLAs is the same as in :current galaxies, a significant fraction of the sky would be covered by emission from low surface-brightness objects. I describe results of a recent survey for such emission using deep images from the Hubble Ultra Deep Field. The low rate of detection implies a low efficiency for in situ star formation throughout the neutral gas. But evidence that the gas emits cooling radiation suggests it is being heated. I discuss why in DLAs with cooling rates below a critical value the gas is heated by FUV background radiation, and in DLAs with cooling rates above the critical value local sources of FUV radiation are required. The local sources are likely to be compact Lyman Break galaxies (LBGs) embedded in the DLA gas. I discuss evidence that the critical cooling rate divides the DLA sample into two distinct populations with different physical properties.
May 16, 2007 | 3:30 PM | RI 480 Three Mysteries of Matter Marcela Carena, Fermilab
Particle physicists are on the verge of a direct experimental look at the mysterious Higgs field, which allegedly gives mass to all the elementary particles. Beyond the Higgs, other mysteries of matter face us, such as the identity of dark matter and the origin of the baryon asymmetry of the universe, both of which require new laws of physics beyond the Standard Model. I will summarize our present theoretical understanding of how these mysteries may be related within the context of TeV-scale Supersymmetry, and discuss experimental probes of this scenario.
May 30, 2007 | 3:30 PM | RI 480 The SDSS Supernova Survey Rick Kessler, The University of Chicago
March 23, 2007 | 12:00 PM | LASR Conference Room What's the Trouble with the Anthropic Principle? Roberto Trotta, Oxford University
Anthropic arguments based on selection effects for observers have been claimed to successfully explain the measured value of the cosmological constant. In this talk I review the foundation of such claims in the context of probability theory and show that different (and equally legitimate) ways of assigning probabilities to candidate universes lead to totally different anthropic predictions. As an explicit example, I discuss a weighting scheme based on the total number of possible observations that observers can carry out over the entire lifetime of the Universe. I show that this leads to an extremely small probability for observing a value of the cosmological constant equal to or greater than what we now measure, in marked contrast with the usual result. I also discuss principles of consistent probabilistic reasoning, showing that the anthropic principle as applied in most of the literature is logically inconsistent. I conclude that current implementations of the anthropic principle display a worrisome lack of predictivity, and cannot be used to explain the value of the cosmological constant, nor, likely, any other physical parameters.
March 30, 2007 | 12:00 PM | LASR Conference Room Ultrahigh Energy Cosmic Neutrinos Ina Sarcevic, University of Arizona
Ultrahigh energy (UHE) astrophysical neutrinos that originate in interactions of cosmic rays with the microwave background radiation, or from astrophysical sources such as Active Galactic Nuclei (AGN) and Gamma Ray Bursts (GRBs), provide a unique way of studying astrophysics as well as particle physics. I will discuss what we can learn from UHE cosmic neutrinos. I will show that the effect of neutrino oscillations is production of tau neutrinos which can provide an enhanced signal for the detection of cosmic neutrinos. Furthermore, interactions of UHE cosmic neutrinos could potentially lead to the production of microscopic black holes predicted in theories of extra dimensions, or they may produce supersymmetric charged particles that travel large distances, such as sleptons. I will discuss these processes and their signals in neutrino detectors such as Auger, Anita, IceCube, EUSO and OWL.
April 6, 2007 | 12:30 PM | LASR Conference Room Exploring the High Energy Universe: GLAST Mission and Science Julie McEnery, NASA/GSFC
The Gamma-ray Large Area Space Telescope (GLAST), scheduled for launch in late 2007, is a satellite based observatory to study the high energy gamma-ray sky. There are two instruments on GLAST: the Large Area Telescope (LAT) which provides coverage from 20 MeV to over 300 GeV, and the GLAST Burst Monitor (GBM) which provides observations of transients from 8 keV to 30 MeV. GLAST will provide well beyond those achieved by the highly successful EGRET instrument on the Compton Gamma-Ray Observatory, with dramatic improvements in sensitivity, angular resolution and energy range. The very large field of view will make it possible to observe ~20% of the sky at any instant, and the entire sky on timescales of a few hours. In addition to the science opportunities, this talk describes the design and expected performance of the instruments, the opportunities for guest investigators, and the mission status.
April 20, 2007 | 12:00 PM | RI 480 Mega-masers, Hubble Constant and Dark Energy Fred K. Y. Lo, National Radio Astronomy Observatory
In contrast to laboratory environments, cosmic conditions allow water maser emission to arise naturally. Powerful water maser emission (water mega-masers) can be found in accretion disks in the nuclei of some galaxies. Besides providing a measure of the mass at the nucleus, such mega-masers can be used to determine the distance to the host galaxy, based on a kinematic model. Such mega=masers are useful for determining the Hubble Constant, independent of the traditional approach based on Cepheid variables. We will explain the importance of determining the Hubble Constant to high accuracy for constraining the equation of state of Dark Energy and describe the Mega-maser Cosmology Project that has the goal of determining the Hubble Constant to better than 3%. Time permitting, we will also present the scientific capabilities of the current and future NRAO facilities for addressing key astrophysical problems.
April 27, 2007 | 12:00 PM | LASR Conference Room Imprints of Tachyonic Preheating on the CMB James M. Cline, McGill University
We have recently proven that the fluctuations of a tachyonic field, which arise at the end of hybrid or brane-antibrane inflation, can act as a source of density perturbations at second order in cosmological perturbation theory. This typically results in a very blue (n=4) contamination of the power spectrum at small scales, as well as nongaussianities. The effect gives rise to powerful new constraints on the parameter space of hybrid-like inflation models, as well as the possibility of new features in the power spectrum.
May 4, 2007 | 12:00 PM | LASR Conference Room Kinematics of the Ultra-Faint Milky Way Dwarf Galaxy Satellites Marla Geha, Herzberg Institute of Astrophysics
In the past year alone, the number of satellite galaxies around the Milky Way has doubled. These newly discovered dwarf galaxies have surface brightnesses and luminosities that are an order of magnitude lower than any previously known galaxy. I present Keck/DEIMOS spectroscopy for eight of these new objects. All are highly dark matter-dominated with mass-to-light ratios of several hundred. The measured velocity dispersions of these galaxies are inversely correlated with their luminosity, indicating that a minimum mass for luminous galactic systems has not yet been reached. I will discuss the importance of these dwarf galaxies in a cosmological context.
May 11, 2007 | 12:00 PM | LASR Conference Room Is the low l CMB cosmic? Glenn d Starkman, Case Western Reserve University
The Cosmic Microwave Background Radiation is our most important source of information about the early universe. Many of its features are in good agreement with the predictions of the so-called standard model of cosmology -- the Lambda Cold Dark Matter Inflationary Big Bang. However, the large-angle correlations in the microwave background exhibit several statistically significant anomalies compared to the predictions of the standard model. Not only is there a lack of large angle correlations, but the lowest multipoles seem to be correlated with each other, rather than statistically independent. Indeed, they also seem to be correlated with the geometry of the solar system, suggesting that what little power there is on large scales is locally not cosmologically produced.
May 18, 2007 | 12:00 PM | LASR Conference Room Determining the Nature of Dark Matter with Astrometry Louie Strigari, UC Irvine
The dwarf spheroidal satellite population of the Milky Way provides an ideal laboratory for studying structure formation on small scales and testing the nature of dark matter. Observationally, their proximity allows for kinematic studies of individual stars. Theoretically, their small masses make them ideal candidates for prominent warm dark matter cores. I will discuss how the present data is able to shed light on the 'missing satellites problem' in cold dark matter, and how future astrometric data will reveal the presence of dark matter cores or cusps in these systems.
May 25, 2007 | 12:00 PM | LASR Conference Room Searching for Stochastic Gravitational Wave Background with LIGO: Results and Implications Vuk Mandic, Caltech
The Laser Interferometer Gravitational-wave Observatory (LIGO) has built three multi-km scale interferometers, designed to search for gravitational waves (GW). One of the targets for these searches is the stochastic GW background, whose existence is expected both due to cosmological and due to astrophysical sources. We discuss the status of LIGO, the most recent results of the search for stochastic GW radiation with LIGO interferometers, and the implications of these results for some of the theoretical models of stochastic GW background.
June 1, 2007 | 12:00 PM | LASR Conference Room ALPACA: A Uniquely Powerful & Inexpensive Deep Imaging Survey Arlin P. Crotts, Columbia University
ALPACA (Advanced Liquid-mirror Probe of Astrophysics, Cosmology and Asteroids) is an 8m-class telescope planned for Cerro Tololo, Chile which will survey a roughly 1000 square degree patch of sky to superlative depth, half of the field imaged each night. This can be done at extremely low cost yet provide uniquely sensitive data on supernovae, active galactic nuclei, variable stars, asteroids and many other classes of objects. ALPACA takes advantage of recent advances in liquid mirror technology, which we will also discuss.
June 8, 2007 | 12:00 PM | LASR Conference Room Cosmological Non-Gaussianity SABINO MATARRESE, UNIVERSITY OF PADOVA, ITALY
Cosmological perturbations have been traditionally assumed to be initially Gaussian. The main reason for this assumption is a simplicity criterion which ascribes the coherent structures in the universe today to the non-linear action of gravitational instability. A theoretical basis for this simplicity assumption comes from single-field slow-roll models of inflation, which predict that curvature perturbations were generated by quantum vacuum fluctuations of a scalar field. These perturbations are almost Gaussian as a consequence of the flatness of the inflaton potential, non-linearities (non-Gaussianities) being suppressed by the smallness of the inflaton self-coupling. However, a large variety of alternative models has been proposed during the last ten years, which generally predict that larger deviations from Gaussianity are possible. One of the most important goals of modern cosmology has then become that of trying to either detect or constrain primordial Non-Gaussianity (NG). I will describe how theoretical predictions of NG and the search for primordial NG signatures in cosmological datasets has become a new and very promising way to discriminate among different models for the origin of primordial perturbations.
March 28, 2007 | 11:00 AM | RI 480 The MAXIPOL CMB Experiment Joseph Zuntz, Imperial College, London
MAXIPOL was a balloon-borne CMB experiment designed to measure the EE polarization power spectrum using a rapid polarization modulator. I discuss the experiment and its results, with emphasis on the Bayesian pipeline used for power spectrum estimation from the sky maps. I also briefly discuss a novel MCMC-based analysis method called 'Baby and Toy' that we are presently developing.
April 16, 2007 | 3:00 PM | LASR Conference Room The Elemental Composition of High-Energy Cosmic Rays: Measurements with TRACER Patrick "Jojo" Boyle, University of Chicago
TRACER (Transition Radiation Array for Cosmic Energetic Radiation) is a large instrument for direct, balloon borne measurements of single element heavy cosmic ray nuclei (boron to iron) in the energy range from 10^10 to several 10^14 eV per nucleus. TRACER has completed long duration balloon flights in Antarctica (2003) and Sweden-Canada (2006). I will present the energy spectra obtained in the 2003 flight and compare our results with previous data of our group and of others, including recent air-shower interpretations, and will discuss the data in the context of current models of acceleration and galactic transport of cosmic rays.
April 23, 2007 | 3:00 PM | LASR Conference Room Advancing Cherenkov Technology and What's 'Nu' in the Mediterranean Richard White, University of Leeds
Imaging atmospheric Cherenkov telescopes (IACTs) probe the universe at energies beyond those available to space based detectors. Even with the improvements in sensitivity provided by new instruments, like VERITAS, the fundamental limits of the technique have not yet been reached. New technology for the current and next generation of IACTs will help to extend the energy range, increase the sensitivity, improve the angular resolution, and open the window to non-IACT physics such as the measurement of the CR spectrum through direct Cherenkov light and intensity interferometry. Advances in IACT technology may also prove suitable for underwater neutrino detectors (UNDs) such as Antares and the proposed cubic-kilometre detector, KM3NeT. In this seminar I will review the state of neutrino astronomy in the Mediterranean, outlining the challenges in constructing a ~200 MEuro detector miles under the ocean and presenting upper limits on the expected neutrino flux from gamma-ray measurements of Blazars. Could it be that we need >>1km3? I will discuss advances in technology for IACTs and UNDs focusing on: analogue fibre-optic signal transmission, high-speed topological triggering and the parallel distribution of digital optical signals.
April 24, 2007 | 12:15 PM | RI 480 The ATA-42: Life, the Universe, and a Wide-angle, Panchromatic Radio Camera for SETI and Radio Astronomy Jill C Tarter, SETI Institute
The first 42 elements of the Allen Telescope Array (ATA-42) are beginning to deliver data. We are scrambling to capitalize on all of the flexibility designed into this innovative instrument for conducting surveys of the astrophysical sky simultaneously with surveys for distant technological civilizations. According to Jerry Ostriker (Plumian Professor, Cambridge; Professor of Astrophysics, Princeton; Provost, Princeton), "Surveys aren't just something that astronomers do, they are the only thing astronomers do." These words are understandable, given Prof. Ostriker's intimate association with the Sloan Digital Sky Survey that is presently transforming our view of the optical universe. The ability to systematically survey one quarter of the sky, with the dynamic range and spatial resolution to zoom in to study individual objects, is providing us with the first truly 3-dimensional map of the nearby cosmos. The optical portion of the spectrum unveils the moderately energetic and hot components of the universe, but the physics of the cool constituents is probed at radio wavelengths. Eventually, the ATA will consist of 350 radio telescopes, each 6.1 m in diameter. The ATA will do for the radio sky what the Sloan Digital Sky Survey has done for the optical sky. Moreover, it will survey so rapidly that it will also provide the first systematic look at the transient radio universe. The ATA delivers simultaneous access to any frequency between 500 MHz and 11.2 GHz, with four separate frequency channels feeding a suite of signal processing backends that can produce wide-angle radio images of the sky in 1024 frequency channels, and at the same time, study up to 32 point sources of interest within its large field of view. This new approach to commensally sharing the sky allows SETI (the Search for ExtraTerrestrial Intelligence) and traditional radio astronomical science to be on the air nearly all the time: our tools are beginning to be commensurate with the size of the vast explorations of the radio sky that we wish to undertake.
May 14, 2007 | 3:30 PM | LASR Conference Room Integrated New Media Outreach for Research Science or How to Make a Podcast that People Will Listen To Aaron Price, AAVSO / Tufts University
Astronomy & Cosmology are uniquely positioned to take advantage of new media outreach channels and techniques (e.g., podcasting, YouTube, blogging, videoblogging, Second Life, etc.). However, these new opportunities require time and an understanding of the cultures that drive them. This talk will provide a crash course in new media (What is it?, How to work with it? Who uses it?). It will also present a case study of a successful outreach approach that integrates new media technologies into existing outreach activities in a way that builds on work already done and respects the audience we're trying to reach.
June 13, 2007 | 11:00 AM | LASR Conference Room Double Trouble: The Lithium Problems Tijana Prodanovic, University of Novi Sad, Serbia
Abstract: In the past few years the lithium nucleosynthesis theories have been put to test with new observations that cannot be fully explained within them. In the light of the discrepancy between the observed 7Li plateau and WMAP-determined primordial 7Li, I will in this talk demonstrate that this discrepancy must become even larger once the pre-Galactic cosmic-ray population like structure-formation cosmic-rays enter in the picture. Moreover, I will argue that the standard 6Li cosmic-ray nucleosynthesis models cannot explain the observed solar 6Li without demanding a too high extragalactic gamma-ray background, which follows from the connection between the 6Li and hadronic gamma-rays. This connection at some point requires normalization to the Milky Way, which, given the long standing problem of unexplained "GeV excess", presents a possible loophole. Thus, I will finally show how recent TeV measurements can be used to better constrain the pionic component to the diffuse gamma-ray spectrum.
March 28, 2007 | 3:30 PM | RI 480 Star Formation as probed by Spitzer Daniela Calzetti, University of Massachusetts
Recent science results from the Spitzer Infrared Nearby Galaxies Survey (SINGS) will be reviewed. In particular, the unprecedented angular resolution of Spitzer has enabled the investigation of the mid-IR emission as a tracer of star formation both of and within galaxies. One immediate application of the mid-IR tracers is to the spatially-resolved Schmidt Law, which I will discuss for the specific case of the nearby galaxy M51. Applicability of the mid-IR SFR tracers to samples of galaxies at cosmological distances will be also discussed.
April 11, 2007 | 3:30 PM | RI 480 Recent results from the SDSS Lens + ACS survey Scott Burles, MIT
I'll present some of the latest results from our (SLACS) survey for galaxy-galaxy strong gravitational lenses discovered by following up the spectroscopic survey of SDSS with direct ACS imaging. As the largest lens survey, we have confirmed more than 87 multiply imaged systems with a myriad of image configurations. This unique and homogeneous data set constrains the intrinsic properties of the lensing galaxies and allows us to construct a more "fundamental" plane of early-type galaxies.
April 18, 2007 | 3:30 PM | RI 480 Injection of Small Bodies into the Interstellar Medium by Planetary Nebulae Bob O'Dell, Vanderbilt University
Recent studies of the nearest planetary nebulae using the Hubble Space Telescope indicate much and perhaps most of the material ejected by intermediate mass stars during the planetary nebula phase is trapped into dense knots of planetary mass. I will report on a detailed study of these knots in the nearest bright planetary nebula, NGC 7293-the Helix Nebula. Using data spanning x-ray to radio wavelengths, we have been able to establish the basic characteristics and the physics governing the knots. We have been able to establish the source of the intense luminosity of these knots in the ubiquitous H2 molecule. The tantalizing question that remains is whether or not these condensations survive in the Interstellar Medium and play a role in the formation of stars and planets.
April 25, 2007 | 3:30 PM | RI 480 Echoes of Galaxy Assembly: Faint Light Around Nearby Galaxies Julianne Dalcanton, University of Washington
Galaxies are not simple superpositions of disks and spheroids. Instead, most disk galaxies host multiple faint stellar components. Studies within the Milky Way suggest that these additional components are old and chemically unevolved, and that they trace distinct epochs in the early history of the Galaxy. I will discuss recent work on the structure, kinematics, and stellar populations of thick disks and stellar halos, and the important constraints that they place on the assembly of disk galaxies.
May 23, 2007 | 3:30 PM | RI 480 Probing the Extremes of Surface Brightness at the Faint End of the Galaxy Luminosity Function Ron Marzke, San Francisco State University
Models of structure formation based on cold dark matter generate a mass spectrum of dark-matter halos that is much steeper than the mass function of observed galaxies. In environments comparable to the Local Group, this “missing satellite” problem is particularly acute for satellite masses below approximately a hundred million solar masses, where the evolution of satellite galaxies is complex, and where the observations are least certain. I will discuss how two ongoing surveys targeting galaxies at opposite extremes of surface brightness are probing the evolution of faint satellite galaxies in environments ranging from low-mass groups to the most massive clusters of galaxies.
June 6, 2007 | 3:30 PM | RI 480 Some Uses of Gravitational Lensing Roger D. Blandford, Kavli Institute for Particle Astrophysics and Cosmology at Stanford University
The first proposed use of gravitational lenses was to measure the Hubble constant. Recent measurements are consistent with those obtained from other determinations and the challenge is to reduce the systematic error on selected sources. Attempts to do this for the source B1608+656 will be discussed and prospects for application to a larger sample will be considered. A more recent proposal to use weak lensing of the clustering of the faintest "galaxies" -- to help understand their redshift distribution, physical properties and role in galaxy formation -- will be described.
May 15, 2007 | 2:00 PM | LASR Unsolved Problems of Magnetoplasma Turbulence Roald Sagdeev, University of Maryland
Many of Space- and Astro- Physics related problems force to go beyond classical Kolmogoroff Turbulence. The whole class of "Dispersive Turbulence" in Hamiltonian Media required the "Weak Turbulence" approach, introducing ensemble of quasiparticles=waves. Nonlinear evolution of spectra often lead to self-generation of large scale flows representing purely classical analog of Bose-Einstein condensation. Among specific applications: "MHD"-Turbulence associated with Galactic Cosmic Ray Shocks, Solar Wind induced non-linear structures.
June 8, 2007 | 9:00 AM | RI 480 Spitzer observations of star- and planet-forming regions: From ice cold to steaming hot Ewine van Dishoeck, Leiden Observatory, The Netherlands
The earliest stages of star- and planet formation are obscured by tens to hundreds of magnitudes of extinction. Observations of the gas and dust at long wavelengths often provide the only way to obtain information on the physical and chemical processes that occur deep inside these regions. In this talk, an overview of Spitzer spectroscopic observations of ices, silicates, PAHs and hot gases will be given. Spitzer has opened up the possibility to obtain high quality mid-infrared spectra for large numbers of low-mass protostars and disks around solar-mass pre-main sequence stars for the first time. The results will be placed in the context of other space- and ground-based data and analyzed using models of protostellar envelopes and (flaring) disks. The diagnostic values of the various lines and bands will be emphasized, and the importance of laboratory data to interpret them will be illustrated. The prospects for future facilities, in particular the Herschel Space Observatory, the James Webb Space Telescope and the Atacama Large Millimeter Array, will be discussed.
June 8, 2007 | 10:30 AM | RI 480 Deconstructing Nearby Galaxies Tim de Zeeuw, Leiden Observatory
Much world-wide effort is devoted to the study of the formation and evolution of galaxies, ranging from observations of the most distant objects in the early Universe to detailed analysis of the motions of individual stars in the Milky Way, combined with theoretical work and numerical simulations. Recent developments in optical instrumentation make it possible to measure the motions and physical properties of stellar populations in nearby galaxies, and to determine the properties of the supermassive black holes in their centres. A representative survey of nearby early-type galaxies and spiral bulges with SAURON, a panoramic integral-field spectrograph custom-built for the UK/NL/E 4.2m William Herschel Telescope on La Palma, reveal a fascinating diversity of properties. The observed stellar and gaseous kinematics and the line-strength distributions provide the intrinsic shape of the galaxies, their orbital structure, the mass-to-light ratio as a function of radius, the frequency of kinematically decoupled cores, the masses of nuclear black holes, and the relation between orbital structure and the age and metallicity of the stellar populations. This 'fossil record' provides key insight into the galaxy formation process. The talk will summarize the main results of the SAURON survey, and briefly consider the next steps, including the possibilities provided by instrumentation on 8m class telescopes.