March 26, 2008 | 3:30 PM | RI 480 | Wednesday colloquium The echo of Einstein's greatest blunder Martin White, UC Berkeley
The coupling of baryons and photons by Thomson scattering in the early universe leads to a rich structure in the power spectra of the cosmic microwave background photons and the matter. The study of the former has revolutionized cosmology and allowed precise measurement of a host of important cosmological parameters. The
study of the latter is still in its infancy, but holds the potential to constrain the nature of the dark energy believed to be causing the accelerated expansion of the universe. I will discuss how we can measure this cosmic sound, and the theoretical developments that need to be made before we can realize the promise of future missions.
April 2, 2008 | 3:30 PM | RI 480 | Astronomy Colloquium Mapping the Dark Universe with Absorption Line Spectroscopy Hsiao-Wen Chen, The University of Chicago
I will discuss what we have learned about the intergalactic medium and interstellar medium in the young universe through absorption line spectroscopy of distant sources.
April 9, 2008 | 3:30 PM | RI 480 | Wednesday colloquium Measuring CMB Polarization James J Bock, California Institute of Technology
The Inflationary paradigm has been remarkably successful in passing observational tests, largely from Cosmic Microwave Background temperature anisotropy measurements. Gravitational waves produced during the epoch of Inflation may imprint a detectable polarization signal in the CMB. This polarization signal, which has a distinctive 'B-mode' pseudo-vector field that cannot be duplicated by matter over/under-densities, depends on the physics of Inflation and thus can be used to distinguish among Inflationary models.
We have developed the BICEP (Background Imaging of Cosmic Extragalactic Polarization) experiment to measure degree-scale CMB polarization in a search for evidence of an inflationary gravitational wave background. I discuss the unique design of the receiver and its performance after two seasons of observations from the South Pole. Recent advances in antenna-coupled TES bolometers will enable significant improvement in system sensitivity. We are developing two new instruments based on these new detectors, SPIDER to measure large-scale polarization from a long-duration balloon, and BICEP2 to deeply integrate in a small region of the sky with low Galactic foregrounds from the ground. These measurements will ultimately culminate in a space-borne measurement with large detector arrays, NASA's Einstein Inflation Probe.
April 16, 2008 | 3:30 PM | RI 480 | Astronomy Colloquium Preliminary SNLS 3rd Year Results Ray Carlberg, University of Toronto
The Supernova Legacy Survey (SNLS) is primarily designed to measure the Dark Energy "equation of state parameter" w. The measurement relies on determining the brightness of supernovae with redshift. The goal is to obtain a precision of about 5% in w, which requires controlling flux measurement errors to a level of about 2%. A secondary goal is to be able to characterize the supernova host galaxy population to better understand the astrophysics of supernovae. The SNLS photometric data is obtained from four color, "every 5 nights" images taken with the Megaprime Camera at the CFHT. Spectra to type the supernovae and obtain redshifts are acquired at Gemini, VLT and Keck. Better methods, combined with more data, allow us to reduce our statistical error by about one third from our first year results. Allowance for systematic errors both increases the errors and shifts the point of best fit. A current complication is the necessity to compare to low redshift measurements in the Landolt photometric system, which will be greatly reduced once low redshift data in the SDSS system become available. These measurements are complementary to the CMB and BAO measurements and lead to improved constraints on cosmology.
April 23, 2008 | 3:30 PM | RI 480 | Wednesday colloquium Star Formation in Turbulent Molecular Clouds Andreas Michael Burkert, University of Munich
Star formation, despite its importance, is not well understood up to now. This situation is however changing quickly. High-resolution observations now provide detailed insight into the complex structure of the turbulent interstellar medium and its various gas phases. The star formation history of molecular cloud regions like Taurus and Orion has now been investigated in great details. At the same time, numerical simulations have achieved enough resolution and complexity in order to explore the origin of turbulent molecular clouds and their fragmentation into stars and stellar clusters in great details.
At the moment the physics of star formation is still in an early phase of exploration. A major step forward has recently been made by identifying several key questions which need to be solved to make progress. I will discuss some of the most puzzling and challenging questions. I then will present recent ideas and and new numerical simulations that have the potential to solve some of these puzzles and by this provide crucial steps towards a consistent theory of star formation.
April 30, 2008 | 3:30 PM | RI 480 | Astronomy Colloquium Binary Compact Objects and their Powerful Astrophysics Vicky Kalogera, Northwestern University
Close binary systems harboring two compact objects play a prominent role in a wide range of astrophysics areas, powering some of the most energetic events in nature. In this talk I will highlight their prominence in the context of gravitational-wave searches and the quest for uncovering the origin of gamma-ray bursts. I will review our current understanding of the formation frequency of binary compact objects, their expected gravitational-wave signatures and the challenges facing gravitational-wave astronomy. I will also discuss how studies of formation and evolution of binary compact objects couple to the star formation history in the nearby Universe and potentially provide an explanation of current gamma-ray burst observations.
May 7, 2008 | 3:30 PM | RI 480 | Wednesday colloquium Searching for Dark-Matter Axions Leslie Rosenberg, University of Washington
The axion is a hypothetical elementary particle whose existence would explain the baffling absence of CP violation in the strong interactions. It's properties make it a good dark-matter candidate. Even though dark-matter axions would make up the overwhelming majority of mass in the universe, they are extraordinarily difficult to detect. We have developed a detector of dark-matter axions that is at heart an exquisitely sensitive detector of microwave radiation. This colloquium will briefly review the role of axions in particle and astrophysics, and will describe the progress we've made in the experimental search.
May 14, 2008 | 3:30 PM | RI 480 | Astronomy Colloquium The Formation and Evolution of a Cosmological Population of Black Holes and Galaxies Tiziana Di Matteo, Carnegie Mellon
There is a growing observational evidence for a close connection between the formation and evolution of galaxies and of their central supermassive black holes. Motivated by this connection, we investigate the coupled formation and evolution of black holes and galaxies using state-of-the-art cosmological hydrodynamic simulations of structure formation in the Lambda-Cold Dark Matter model. Along with the gravitational evolution of dark matter, gas dynamics, cooling and star formation, the simulation follows black hole growth and associated feedback self-consistently. I will discuss black hole growth in the centers of galaxies and the impact of AGN feedback on different aspects of galaxy formation.
May 21, 2008 | 3:30 PM | RI 480 | Wednesday colloquium New CMB Polarization Results from QUaD Clement Pryke, The University of Chicago
Measurements of the intensity fluctuations of the Cosmic Microwave Background have already taught us an enormous amount about the nature of the Universe in which we live. Polarization measurements have the potential to tell us even more. After briefly reviewing the motivation for polarization measurements I will move on to the QUaD experiment at South Pole, which is currently the world's most sensitive CMB polarimeter in the multipole range 200 to 2000. I will describe the instrument, observation strategy, analysis and newly released results. Finally I will mention a new project called SPUD and the push to detect the gravitational wave B modes.
May 28, 2008 | 3:30 PM | RI 480 | Astronomy Colloquium TBA Josh Grindlay, Harvard University
June 4, 2008 | 3:30 PM | RI 480 | Wednesday colloquium CN-cycle Solar Neutrinos and the Solar System Metalicity Wick C Haxton, INT, University of Washington
The CN-cycle plays a modest role in solar energy generation, but produces a significant flux of neutrinos that will be measured in SNO+ and other future detectors. Because past measurements have precisely calibrated other conditions in the solar core -- and because of progress made in constraining neutrino flavor physics -- I argue this new measurement will determine the primordial solar core abundances of C and N to 10%. This will eliminate a key assumption in the standard solar model, and address the current conflict between helioseismology and photospheric abundance determinations. I discuss the possibility that this conflict is real and associated with late-stage metal differentiation in the solar-system disk associated with planetary formation -- and point to observational implications.
June 11, 2008 | 3:30 PM | RI 480 | Astronomy Colloquium The growth of Large-scale Structure from a perspective of 25 years: from CFA1 to DEEP2 Marc Davis, University of California, Berkeley
25 years ago we thought we knew quite a bit about galaxy clustering, but the first redshift surveys showed just how primitive our knowledge was. In the intervening years enormous changes in technology have made it possible to greatly advance our understanding of large-scale structure, and I will briefly review the the advance of knowledge from my personal perspective. I summarize the recent progress made with the DEEP2 survey on the Keck telescope, a fantastic tool to study galaxies, and galaxy clustering, at redshift one. We have now finished this survey, and as expected from the collection of enormous data sets, we find many unanticipated surprises.
Blind surveys for galaxy clusters and anisotropy using the Sunyaev-Zeldovich effect are one of the new frontiers in cosmology, promising to tell us about both about global cosmological parameters as well as cluster formation and astrophysics. We present results from such a survey at 150 GHz using Bolocam, a 144-element mm-wave bolometer camera, on the Caltech Submillimeter Observatory, as well as preliminary maps from a program to observe massive clusters in the SZ effect at high signal-to-noise. Finally, we describe our upcoming MKID camera for the CSO and a prospective follow-up camera on the Cornell-Caltech Atacama Telescope and their expected impact on SZ observations.
April 11, 2008 | 12:00 PM | LASR Conference Room | Friday noon seminar The Atacama Cosmology Michael D Niemack, Princeton University
The Atacama Cosmology Telescope (ACT) is measuring the temperature fluctuations of the Cosmic Microwave Background on arcminute to degree angular scales. Measuring these angular scales will allow us to probe the primary CMB anisotropies as well as explore secondary mechanisms such as the Sunyaev-Zel’dovich effect, the Ostriker-Vishniac effect, and gravitational lensing of the CMB. These measurements combined with follow-up redshift measurements of galaxies will allow us to constrain the dark energy equation of state and the neutrino mass as well as study the growth of structure and the ionization history of the universe. ACT observations began in 2007 with the installation of the Millimeter Bolometer Array Camera (MBAC). During the first season of observations MBAC consisted of a kilopixel detector array of TES bolometers operated at 150 GHz. We are now preparing for the second season of observations by integrating two additiona l detector arrays into MBAC, which will be operated at 220 and 280 GHz.
We will review methods for constraining the dark energy equation of state using ACT observations combined with photometric redshift measurements. Then, we will describe the ACT and MBAC design, development, and status as well as preliminary results from the first season of observations. Finally, we will present the results of a new approach for improving photometric redshift measurements by combining ground-based optical observations with ultraviolet observations from the GALEX satellite telescope.
April 18, 2008 | 12:00 PM | LASR Conference Room | Friday noon seminar CAPMAP results, QUIET prospects, and an inside-outside view of Gravity Wave searches in the CMB Bruce Winstein, The University of Chicago
The CAPMAP experiment recently submitted final results on the Polarization of the Cosmic Microwave Background Radiation at fine angular scales. CAPMAP's methodology will be discussed. The experiment used coherent detectors which are also the basis for QUIET which aims to study the possible Inflationary Gravity Wave Background (GWB). This alternative (to TES Bolometers) and still viable approach will be discussed. The challenges in detecting the GWB are formidable; we'll take a little time to consider if the current approach is the ideal one.
April 25, 2008 | 12:00 PM | LASR Conference Room | Friday noon seminar Origin and Evolution of Magnetic Fields Ellen G Zweibel, U Wisconsin, Madison
Magnetic fields are ubiquitous in astrophysical systems, but despite many years of progress in cosmology, we know very little about how and when they originated, or how they evolve. I will review traditional and nontraditional evidence for magnetic fields and discuss key processes in their maintenance and evolution.
I will present new results from five years of WMAP observations. The WMAP satellite measures the Cosmic Microwave Background temperature and polarization anisotropy over the whole sky. With five years of data, we detect no significant deviations from the simple LCDM cosmological model: a flat universe filled with baryons, photons, cold dark matter, neutrinos, and a cosmological constant. I will describe the observations, and discuss the cosmological implications for cosmic inflation, for the reionization of the universe by the first stars, and for the contents of the universe including neutrinos and dark energy.
May 16, 2008 | 12:00 PM | LASR Conference Room | Friday noon seminar Black Hole-Bulge Relations Across the Hubble Sequence Jenny E Greene, Princeton
The evolution of supermassive black holes and galaxies are apparently inextricably linked, and we might hope to gain unique insight into the nature of their connection by studying galaxies with currently accreting black holes. The study of active host galaxies has a long history; I focus here on three innovative experiments that exploit both the recent availability of large spectroscopic surveys such as the SDSS and improved techniques to estimate black hole masses in active galactic nuclei (AGNs). The first uses HI observations of local AGNs to measure their neutral gas fractions, dynamical masses, and disturbance levels. The second studies the host galaxies of local obscured AGNs. Because the accretion disk is hidden, it is possible to look for direct evidence of AGN-induced disturbance in the hosts of these intrinsically very luminous systems. Finally, I examine the host galaxies of AGNs selected to have the lowest black hole masses known, a regime in which black hole-bulge relations appear to break down. I discuss the implications for AGN fueling and feedback, and the possibility of observing continuing evolution in the relations between black hole mass and bulge properties at the present epoch.
May 23, 2008 | 12:00 PM | LASR Conference Room | Friday noon seminar Blowing Hot and Cold on Galaxy Clusters Greg Bryan, Columbia University
The new X-ray observatories have unleashed an explosion of data about the hot gas in galaxy clusters, in the process overturning cherished theories and posing new puzzles, particularly about the impact of AGN on the thermal state of the cluster gas. I review what can be understood from observations, simple theory and high-resolution numerical simulations, showing that in some areas the latest observational results are in surprisingly good agreement with theory. On the other hand, the impact of cooling and heating on cluster cores and -- to a lesser extent -- on global scaling relations, is still not well understood. This uncertainty is important when using clusters for constraining cosmological parameters and I will talk about some ways to improve both our understanding of AGN feedback, and our cosmological constraints.
May 30, 2008 | 12:00 PM | LASR Conference Room | Friday noon seminar Results from the SDSS Supernova Survey Richard Kessler, The University of Chicago
I will present an overview of the three-year SDSS Survey that resulted in approximately 500 spectroscopically confirmed SN Ia. Using ~100 SNe Ia from the first season of the SDSS survey, along with another 140 SNe~Ia from other surveys, preliminary results are presented for the cosmological parameters w and Omega_M. Results are compared for both the SALT2 and MLCS methods.
June 6, 2008 | 12:00 PM | LASR Conference Room | Friday noon seminar Dark and Luminous Matter in Clusters of Galaxies Andisheh Mahdavi, University of Victoria
Clusters of galaxies are dominated by dark matter. We can see the gravitational effect of this dark material on the orbits of cluster members, the thermodynamics of the hot gas, and the lensed shapes of galaxies behind the cluster. I will show that combining X-ray, lensing, and SZ data for a single relaxed cluster can yield powerful constraints on its dark matter distribution and on the equation of state of the intracluster plasma. At the same time, multiwavelength observations of merging clusters can yield significant and perhaps even more interesting constraints on dark matter properties. Both relaxed and merging clusters are well-represented in the Canadian Cluster Comparison Project, an X-ray, optical, and radio survey of fifty nearby systems. I will conclude by discussing an unusual, massive, X-ray bright core nearly devoid of galaxies at the heart of Abell 520, and discuss whether it can advance our understanding of the fundamental nature of dark matter.
June 2, 2008 | 2:00 PM | AAC 123 | Special Seminar The WiggleZ Dark Energy Survey Karl Glazebrook, Swinburn University
I will give a short mid-survey report on the WiggleZ survey running on the Anglo-Australian Telescope which aims to be the first spectroscopic survey to detect BAO at high-z. (0.5< z <1)
June 10, 2008 | 12:00 PM | AAC 123 | Special Seminar Low-luminosity starburst galaxies under a GRB afterglow spotlight at high redshift Hsiao-Wen Chen, The University of Chicago
June 13, 2008 | 12:00 PM | LASR 152 | Special Seminar The Transiting Exoplanet Survey Satellite (TESS) George Ricker, MIT (Kavli Institute)
The Transiting Exoplanet Survey Satellite (TESS) is a low cost, SMEX-class planet finder. In a two year all-sky survey, TESS will observe more than two million bright, nearby stars, searching for temporary drops in brightness that are caused by planetary eclipses. These eclipses (or "transits") occur when a planet's orbit carries it directly in front of its parent star. Such transits not only provide the means of identifying the planet, but also provide knowledge of the planet's diameter, mass density, surface gravity, temperature, and other key properties. TESS is expected to catalog more than 1000 transiting exoplanet candidates--20 times as many as are presently known, including a sample of 'super Earths'. The TESS "wide-shallow" survey will be complementary to the "narrow-deep" ones of the Corot and Kepler missions: its sky coverage will exceed that of Corot by 1000 times, and that of Kepler by 400 times. Because the TESS all-sky survey will systematically examine every interesting bright star likely to harbor an exoplanet, the resulting TESS Transit Catalog will constitute a unique scientific legacy. High resolution, follow-up ground-based optical and space-based IR spectroscopy of exoplanets demands bright targets. Thus, TESS should identify those new exoplanets that are ideal for study with the world's largest ground-based telescopes, as well as with NASA's upcoming James Webb Space Telescope. The TESS mission is a collaborative effort led by researchers at MIT, the Harvard-Smithsonian Center for Astrophysics, and the NASA Ames Research Center. Additional TESS partners include the NASA Goddard Space Flight Center, the Harvard Origins of Life Initiative, Lowell Observatory, Caltech's IPAC, the SETI Institute, Geneva Observatory in Switzerland, Tokyo Institute of Technology, SUPAERO in France, ATK Space, Espace Inc, and the privately-funded Las Cumbres Observatory Global Telescope Network. TESS has been accepted for a Phase A study by NASA, and is proposed for launch in early 2012.