Sep 01

"Cosmic Rays and the Quest for New Physics"
Stefano Profumo, University of California, Santa Cruz

Recent cosmic ray data, notably from the Pamela and Fermi satellites, indicate that previously unaccounted-for powerful sources in the Galaxy inject high-energy electrons and positrons. Interestingly, this new source class might be related to new fundamental particle physics, and specifically to pair-annihilation or decay of galactic dark matter. I will discuss how this exciting scenario is constrained by Fermi gamma-ray observations, and which astrophysical source counterparts could also be responsible for the high-energy electron-positron excess. In particular, I will review the case for nearby mature pulsars, and the impact of newly discovered radio-quiet pulsars that pulsate in gamma rays. While high-energy electron-positron measurements sample local (closer than 1 kpc) cosmic rays, diffuse radio and gamma-ray emission informs us about the global galactic cosmic ray population. I will thus offer a few thoughts on recent claims involving the detection of diffuse radio ("WMAP haze") and gamma-ray ("Fermi haze") emissions and on implications for the quest for New Physics.

Sep 08

"Optimizing a ground-based CMB polarization experiment"
Chao-Lin Kuo, Stanford University

I will describe efforts to measure the CMB (cosmic microwave background) B-mode polarization generated by gravitational wave background and gravitational lensing. In particular, I will present the case for the POLAR Array, a large ground-based CMB initiative that will have sufficient collective sensitivity to (1) measure the lensing deflection field via B-mode over a significant part of the sky, and (2) reach good enough sensitivity on a deep field for effective delensing. The pathfinder experiment will be deployed to the South Pole in late 2012.

Sep 22

"The SPM4 Catalog of 100 million absolute proper motions and applications to southern hemisphere galactic kinematics"
William F. van Altena, Yale University

The Yale/San Juan Southern Proper Motion SPM4 Catalog is the culmination of a highly successful 47-year collaboration between the National University of San Juan (UNSJ) and the Yale Southern Observatory (YSO). The SPM4 Catalog contains absolute proper motions, celestial coordinates, blue and visual passband photometry for 103,319,647 stars and galaxies between the south celestial pole and -20 degrees declination. The Catalog is roughly complete to V=17.5 and the precision of its positions and absolute proper motions is approximately 30 to 150 mas and 2 to 10 mas/yr, respectively. It is based on photographic and CCD observations taken with the Yale Southern Observatory's double-astrograph at the Cesco Observatory in El Leoncito, Argentina.

Oct 6

"A Planetarium for Austin: an Historical Perspective"
Torvald Hessel, Austin Planetarium

Austin is the largest city in the U.S. without a planetarium. Studies indicate that planetariums and science museums greatly benefit science education and interest in science as a career path in the areas they serve. With the current push in the U.S. to promote education in science and mathematics, there is no greater time to develop Austin's first Planetarium, Science Museum, and Technology Center. Executive Director of the Austin Planetarium, Torvald Hessel has been at the forefront of the Planetarium movement here in Austin and will be discussing his efforts to develop the Austin Planetarium, Science Museum, and Technology Center facility in downtown Austin, finally giving the central Texas community a place to reach for the stars.

About Our Speaker: Torvald Hessel is the founder of the 501(c)(3) non-profit the Austin Planetarium, and currently serves as the Executive Director and President of the organization. Additionally, he is an adjunct professor of Astronomy at the Austin Community College. A native of the Netherlands, Mr. Hessel received his Masters in Astrophysics from the University of Amsterdam and worked for several years as a lecturer and presenter at Amsterdam's Artis Planetarium. During his time at the Planetarium Mr. Hessel developed planetarium presentations and astronomy lectures aimed at educating people ranging from kindergarten aged children to professional astronomers. After immigrating to the United States in 1999 he worked for Trilogy Software and later as a Senior Systems Analyst for the University of Texas at Austin before committing full-time to the Austin Planetarium. He became a naturalized citizen in 2005. Mr. Hessel is a champion of science education and has provided astronomy themed outreach to a wide range of institutions including Austin ISD, ACC, and the Dell Children's Hospital.

Oct 20

"X-ray Polarization: The Last Frontier in X-ray Astronomy"
Pranab Ghosh, Tata Institute, Mumbai

Exploring the X-ray polarization properties of cosmic X-ray sources like neutron stars, stellar black holes, and active galactic nuclei is widely called the "last frontier" in X-ray astronomy, despite one pioneering detection made three decades ago. This is so because efficient techniques for measuring the polarization of X-ray photons evolved only recently, making it possible to study polarized X-rays from a variety of celestial X-ray sources after a long hiatus. GEMS is a recently-approved NASA mission dedicated to the above study. We outline the essential features of GEMS detectors. We summarize the expected X-ray polarization characteristics of major categories of cosmic X-ray sources like accretion and rotation powered pulsars, magnetars, black holes in X-ray binaries and active galactic nuclei, and supernova remnants. We stress the diagnostic potential of the new parameters offered by polarization studies (polarization amount and direction) in addition to those normally available from timing and spectral studies. We conclude by discussing possibilities of further X-ray polarimetric studies from other X-ray missions of the future.

Nov 10

"Exploring the Dark Universe with Gravitational Lensing"
Carsten Dominik, University of Amsterdam, NL

The innermost regions of protoplanetary disks are free of dust. During the early phases of disk evolution, this dust gap is caused by dust evaporation around about 1500 K. In later stages, other up to no not fully clarified mechanisms start to clear out a larger region in the disk, leading to structures that are called transitional disks. I will discuss a number of physical mechanism that are responsible for the presence and absence of dust in these regions.

Nov 17

"Tracing the Evolution of Dust in Protoplanetary Disks"
Isa Oliveira, University of Leiden, NL

I will present Spitzer IRS mid-infrared (5-35 micrometers) spectra of a complete flux-limited sample of YSOs selected on the basis of their infrared colors in the young Serpens Molecular Cloud. The presence, strength, and shape of different spectral features are used to infer dust properties for these systems, such as composition, crystallinity and grain size distribution, while the mid-IR slope is used as a proxy for disk geometry. The results for the disks in Serpens are compared to those in other star- forming regions with a range in median ages and environment in order to trace the evolution of dust on a bigger scale. These results are ultimately put in context with those of our own Solar System.

Nov 24

"The Atacama Cosmology Telescope: The Present and the Future"
Sudeep Das, University of California, Berkeley

Arcminute resolution observations of the mm-wave sky are changing our view of the cosmic microwave background (CMB) in a fundamental way. Together with mapping out the acoustic features on the Silk damping tail of CMB, data from the Atacama Cosmology Telescope (ACT) are providing new insights into secondary CMB anisotropies and extragalactic point source populations that dominate the scene at small angular scales. A set of recent and upcoming papers showcases the broad spectrum of science coming out of the ACT project: ranging from power spectra, to new constraints on cosmological parameters, to a successful survey of galaxy clusters using the Sunyaev-Zel'dovich effect. In the first part of the talk, I will review these recent developments and give a status report on ACT. Then, I will describe future projects involving the gravitational lensing of the CMB, and the cross-correlation with external datasets. Finally, I will touch upon the prospects for ACTPOL, the version of ACT with polarization capabilities, which is scheduled to see first light in 2012.

Dec 1

"Starburst Galaxies in a Cosmological Context"
Roderik Overzier, Max Planck Institute, Garching

Starburst galaxies are important for our understanding of galaxy evolution, especially at high redshifts when most galaxies formed their stars at a vigorous rate. Although observations now allow us to study basic properties of galaxies up to z~8, the interpretation of these data relies on models that are still difficult to constrain. The study of starbursts in the nearby universe is particularly useful, as they allow us to probe in great detail a range of extreme processes analogous to those that were common only at high redshift. In this talk, I will highlight some of our recent results that shed new light on a number of open problems related to starbursts and their cosmological context. Topics will include the cosmic star formation rate density, the importance of gas accretion and mergers, the relation between outflows and reionization, and the co-evolution of bulges and black holes