4 April 2008	25 April 2008	6 June 2008
11 April 2008	9 May 2008
18 April 2008	23 May 2008

Sunil Golwala, Caltech

SZ Survey Results from Bolocam  

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.

Michael D Niemack, Princeton University

The Atacama Cosmology  

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.

Bruce Winstein, The University of Chicago

CAPMAP results, QUIET prospects, and an inside-outside view of Gravity Wave searches in the CMB  

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.

Ellen G Zweibel, U Wisconsin, Madison

Origin and Evolution of Magnetic Fields  

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.

Joanna Dunkley, Princeton/Oxford

WMAP5: Implications for Cosmology  

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.

Greg Bryan, Columbia University

Blowing Hot and Cold on Galaxy Clusters  

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.

Michael R Blanton, New York University

Testing cold dark matter on  

26 March 2008	23 April 2008	21 May 2008
9 April 2008	7 May 2008	4 June 2008

Martin White, UC Berkeley

The echo of Einstein's greatest blunder  

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.

James J Bock, California Institute of Technology

Measuring CMB Polarization  

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.

Andreas Michael Burkert, University of Munich

Star Formation in Turbulent Molecular Clouds  

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.

Leslie Rosenberg, University of Washington

Searching for Dark-Matter Axions  

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.

Clement Pryke, The University of Chicago

TBA  

Wick C Haxton, INT, University of Washington

CN-cycle Solar Neutrinos and the Solar System Metalicity  

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.

2 April 2008	30 April 2008	28 May 2008
16 April 2008	14 May 2008

Hsiao-Wen Chen, The University of Chicago

Mapping the Dark Universe with Absorption Line Spectroscopy  

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.

Ray Carlberg, University of Toronto

Preliminary SNLS 3rd Year Results  

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.

Vicky Kalogera, Northwestern University

Binary Compact Objects and their Powerful Astrophysics  

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.

Tiziana Di Matteo, Carnegie Mellon

The Formation and Evolution of a Cosmological Population of Black Holes and Galaxies  

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.

Josh Grindlay, Harvard University

Astronomy Colloquium