23 March 2007	27 April 2007	25 May 2007
30 March 2007	4 May 2007	1 June 2007
6 April 2007	11 May 2007	8 June 2007
20 April 2007	18 May 2007

Roberto Trotta, Oxford University

What's the Trouble with the Anthropic Principle?  

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.

Ina Sarcevic, University of Arizona

Ultrahigh Energy Cosmic Neutrinos  

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.

Julie McEnery, NASA/GSFC

Exploring the High Energy Universe: GLAST Mission and Science  

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.

Fred K. Y. Lo, National Radio Astronomy Observatory

Mega-masers, Hubble Constant and Dark Energy  

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.

James M. Cline, McGill University

Imprints of Tachyonic Preheating on the CMB  

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.

Marla Geha, Herzberg Institute of Astrophysics

Kinematics of the Ultra-Faint Milky Way Dwarf Galaxy Satellites  

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.

glenn d starkman, case western reserve university

Is the low l CMB cosmic?  

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.

Louie Strigari, UC Irvine

Determining the Nature of Dark Matter with Astrometry  

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.

Vuk Mandic, Caltech

Searching for Stochastic Gravitational Wave Background with LIGO: Results and Implications  

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.

Arlin P. Crotts, Columbia University

ALPACA: A Uniquely Powerful & Inexpensive Deep Imaging Survey  

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.

SABINO MATARRESE, UNIVERSITY OF PADOVA, ITALY

Cosmological Non-Gaussianity  

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.

4 April 2007	9 May 2007	30 May 2007
2 May 2007	16 May 2007

Gary Hinshaw, NASA Goddard

Three-Year Results from WMAP (with Commentary)  

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.

Steven M. Kahn, Stanford University

Wide-Field Surveys of the Optical Sky: The Large Synoptic Survey Telescope (LSST)  

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.

Arthur M. Wolfe, CASS, University of California, San Diego

Star Formation at High z: Evidence for two types of DLAs?  

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.

Marcela Carena, Fermilab

Three Mysteries of Matter  

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.

Rick Kessler, The University of Chicago

The SDSS Supernova Survey  

28 March 2007	18 April 2007	23 May 2007
11 April 2007	25 April 2007	6 June 2007

Daniela Calzetti, University of Massachusetts

Star Formation as probed by Spitzer  

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.

Scott Burles, MIT

Recent results from the SDSS Lens + ACS survey  

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.

Bob O'Dell, Vanderbilt University

Injection of Small Bodies into the Interstellar Medium by Planetary Nebulae  

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.

Julianne Dalcanton, University of Washington

Echoes of Galaxy Assembly: Faint Light Around Nearby Galaxies  

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.

Ron Marzke, San Francisco State University

Probing the Extremes of Surface Brightness at the Faint End of the Galaxy Luminosity Function  

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.

Roger D. Blandford, Kavli Institute for Particle Astrophysics and Cosmology at Stanford University

Some Uses of Gravitational Lensing  

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.

28 March 2007	23 April 2007	14 May 2007
16 April 2007	24 April 2007

Joseph Zuntz, Imperial College, London

The MAXIPOL CMB Experiment  

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.

Patrick "Jojo" Boyle, University of Chicago

The Elemental Composition of High-Energy Cosmic Rays: Measurements with TRACER  

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.

Richard White, University of Leeds

Advancing Cherenkov Technology and What's 'Nu' in the Mediterranean  

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.

Jill C Tarter, SETI Institute

The ATA-42: Life, the Universe, and a Wide-angle, Panchromatic Radio Camera for SETI and Radio Astronomy  

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.

Aaron Price, AAVSO / Tufts University

Integrated New Media Outreach for Research Science or How to Make a Podcast that People Will Listen To  [Online talk]

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.

13 June 2007

Tijana Prodanovic, University of Novi Sad, Serbia

Double Trouble: The Lithium Problems  

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.