Larry Widrow, Queen's University

The Local Group is a dynamic environment. Its two main constituents, M31 and the Milky Way, are continually accreting smaller galaxies. This process is beautifully captured in the Pan-Andromeda Archeological Survey, which is providing, in unprecedented detail, the structure and content of M31 and M33. Moreover, both M31 and the Milky Way are barred, which suggests that these galaxies are undergoing secular evolution. I will describe simulations that are designed to explore these and other phenomena. A numerical toolbox for generating flexible, equilibrium models of disk galaxies will also be presented.

Hui Li, LANL

Galaxy clusters are important laboratories for cosmology and astrophysics. X-ray and radio observations of galaxy clusters have revealed a wealth of structures in association with extragalactic radio sources. Structures in the form of large-scale cavities and weak shocks provide a reliable gauge of the energy output of extragalactic radio jets launched by AGNs. Furthermore, they place interesting constraints on the nature of AGN outflows, especially on large scales. We will present 3-D MHD simulations of jets/lobes in the ICM and compare them with ~70 X-ray cavities as well as individual jet/lobe sources. In addition, we will present cosmological MHD simulations of galaxy cluster formation with AGN jets/lobes feedback and its implications for the origin and energetics of the cluster-wide magnetic fields. We demonstrate that the ICM turbulence is excited and sustained by the frequent mergers during the cluster formation. We quantify the available turbulent kinetic energy and nonlinear cascade rates. This turbulence excites a small-scale dynamo process that transports and amplifies the fields originated from the radio jet/lobe system. This process could be the primary process of populating the whole cluster with magnetic fields. We describe the properties of magnetic fields, including their strength, spatial distribution, power spectra and saturation mechanism. These simulations can be compared with observations made by VLA, LOFAR, and E-VLA.

Akito Kusaka, The University of Chicago

Cosmic microwave background (CMB) polarization is the ultimate probe of primordial gravity waves in the early universe, via the B-mode (or parity odd) signal on degree angular scales. A detection of such a signal would be strong evidence of the inflation scenario and represent indirect observation of a fundamentally new phenomenon near the grand unification energy scale. With its unique HEMT radiometer technology, QUIET is among the most competitive experiments aiming to detect such a signature in the CMB. QUIET has just completed its observation from October 2008 through December 2010, first with 43GHz receiver and then with 95GHz one, collecting over 10000 hours of data in total. In this talk, I will review the QUIET experiment and report the first result from QUIET using 3458 hours of data taken with the 43GHz receiver. The result is supported by analysis techniques such as cross correlation of the maps with different pointings and the blind analysis. Thoroughly estimated systematic errors, being the least of those reported to date, demonstrate systematic cleanness of QUIET and represent a good prospect for a future project.

Bob Wald, The University of Chicago

CANCELLED

We provide a general framework that allows one to analyze---in a mathematically precise manner---solutions to Einstein's equation wherein, a priori, nonlinear effects of small scale inhomogeneities can produce significant effects on the background geometry. This framework is a generalization (to the case where inhomogeneous matter is present) of the ``shortwave approximation'' that has been used to analyze the back-reaction effects of gravitational radiation. We prove within this framework that, provided that matter satisfies the weak energy condition (i.e. has positive energy density in all frames), the ``effective stress energy" produced by small scale inhomogeneities also must satisfy the weak energy condition and must be traceless, so it cannot mimic the effects of dark energy. We also analyze cosmological perturbation theory within this framework and calculate the corrections produced by small scale inhomogeneities to the equations satisfied by long wavelength perturbations.

Juri Toomre, JILA, University of Colorado at Boulder

Stellar convection zones in most settings should be able to build magnetic fields through dynamo action, especially if the flows are turbulent and the stars rotate. There is much more subtlety as to whether the resulting magnetic fields also exhibit large-scale structure and possible temporal flips and even cycles. We have been studying through 3-D global simulations the nature of both differential rotation and dynamo action that can be achieved in G-type stars like the sun by turbulent convection in their outer envelopes, and also by core convection in more massive A-type stars. The richness of structures realized will be discussed.

Leonardo Senatore, Stanford University

In the past few decades Cosmological observations have allowed us to explore the history of our universe and the nature of the Big Bang with greater and greater precision. They strongly suggest that our Universe started with a period of cosmic acceleration that we call Inflation. I will describe what we currently know about this initial epoch and how, thanks to the upcoming experiments, our knowledge about it might improve drastically, revealing us the dynamics that lead to it and making us extremely confident about the existence of such an epoch at the beginning of our Universe.

Stanislav Boldyrev, University of Wisconsin - Madison

The talk will discuss what is currently known about the properties of incompressible magnetohydrodynamic (MHD) turbulence. The talk will start with a general introduction, and then will review recent analytic developments, numerical simulations, and where possible, observations and experiments. The discussion will include the role of the guide field and the ideal conservation laws, the inherent anisotropies of the turbulent energy cascade, the physics of the "imbalance" or the Alfvenization phenomenon, and the processes of self-organization.

Vikram Dwarkadas, University of Chicago

Supernovae (SNe) are divided into many types and sub-types,but the precise progenitor of each (sub)type of SN still remains unknown. Core-collapse supernovae (SNe) arise from the explosion of massive stars. The resultant shock wave expands in the circumstellar medium formed by mass-loss from the massive star. The interaction of the shock wave with this medium gives rise to X-ray and radio emission.

In this talk we will discuss how circumstellar interaction can be used to constrain the SN progenitor. As a specific example, we will consider SN1996cr, one of the five closest SNe to explode in the past 30 years, yet which lay undiscovered for many years. Our team was awarded a 500,000 sec Chandra HETG observation of the SN, which was completed in early 2009. In order to interpret this data, we have carried out hydrodynamic simulations, followed by computations of simulated X-ray spectra under non-equilibrium ionization conditions, that can be directly compared with the observations. These
calculations allow us to infer the evolution of the SN shock wave, the density structure, and the abundances of the ejecta and surrounding medium, to reasonable accuracy. We will show how the data allow us to constrain the progenitor properties. The deep spectra even allow us to investigate the 3D morphology of this point source by studying the
detailed line shapes. We will discuss the implications for massive star mass-loss and SN evolution.

Dennis Zaritsky, University of Arizona

Unlike the theory of stellar structure, which has a simple and intuitive outline, that of galactic structure is piecemeal and ad hoc. In fact, it has been difficult even to determine whether or not one should expect there to be such an analog. Numerical modeling of the problem grows ever more sophisticated and detailed in its efforts to match observations, suggesting that perhaps the problem is beyond any simple description. However, I will, using simple and general arguments, demonstrate that the global structure of galaxies of all sizes, masses, and morphological types can be described to a high degree using only two observational parameters. I will then explore the nature of those two parameters.

Nir J. Shaviv, Racah Inst. of Physics, Hebrew University

Recent measurements of the positron/electron ratio in the cosmic ray (CR) flux exhibits an apparent anomaly, whereby this ratio increases between 10 and 100 GeV. This has triggered significant excitement as it can be interpreted as evidence for dark matter decay. I will show instead that the standard source for cosmic rays, that of supernova remnants, explains this ''anomaly'' once one considers the actual inhomogeneous distribution of SNe in the disk. This also explains other cosmic ray characteristics, such as the energy dependence of the Boron to Carbon ratio.

Chris Carilli, NRAO

Deep optical and near-IR surveys have traced the star formation history of the Universe as a function of environment, stellar mass,and star formation rate, back to cosmic reionization and the first galaxies (z > 6). While progress has been truly impressive, near-IR studies of early galaxies are fundamentally limited in two ways: (i) obscuration of rest-frame UV emission by dust, and (ii) near-IR studies reveal only the stars and ionized gas, thereby missing the evolution of the cool gas in galaxies, the fuel for star formation. Line and continuum studies at radio wavelengths (cm through submm) address both these issues, by probing deep into the earliest, most active, and dust obscured, phases of galaxy formation, and by revealing the molecular and cool atomic gas. I will summarize the techniques of radio astronomy to perform these studies, then present two recent examples. The first will consider the atomic and molecular gas, dust, and star formation, in the host galaxies of z ~ 6 quasars. The host galaxies are under-going extreme starbursts, with star formation rates > 1000 Mo/year, and molecular gas masses in excess of 1e10 Mo. Through gas dynamics, we can estimate the ratio of the bulge mass to black hole mass. These observations imply that we are witnessing the co-eval formation of massive elliptical galaxies, and super-massive black holes, within 1 Gyr of the Big Bang. The second entails observations of normal galaxy formation during the 'epoch of galaxy assembly' (z ~ 1.5 to 2.5). These observations reveal massive gas reservoirs without hyper-starbursts, and that active star formation occurs over a wide range in galaxy stellar mass. We find that the peak epoch of star formation in the Universe also corresponds to an epoch when the baryon content of galaxies was dominated by molecular gas, not stars. I will conclude with a description and status report of the Atacama Large Millimeter Array, and the Expanded Very Large Array. These telescopes represent an order of magnitude, or more, improvement over existing observational capabilities from 1 GHz to 1 THz, promising to revolutionize our understanding of galaxy formation.

Andrea Ghez, UCLA

The proximity of our Galaxy's center presents a unique opportunity to study a galactic nucleus with orders of magnitude higher spatial resolution than can be brought to bear on any other galaxy. After more than a decade of astrometry from diffraction-limited speckle imaging on large ground-based telescopes, the case for a supermassive black hole at the Galactic center has gone from a possibility to a certainty, thanks to measurements of individual stellar orbits. The advent of adaptive optics technology has significantly expanded the scientific reach of our high-spatial-resolution infrared studies of the Galactic center. In this talk, I will present the results of several new adaptive optics studies on (1) our current understanding of the galaxy's central gravitational potential, (2) the puzzling problem of how young stars form in the immediate vicinity of the central black hole, (3) the surprising, apparent absence of the predicted central stellar cusp around the central supermassive black hole (an essential input into models for the growth of nuclear black holes), and (4) how future large ground-based telescope may allow these studies to test general relativity and cosmological models.

Hsiao-Wen Chen, University of Chicago

Gamma-ray bursts are among the most energetic events in the universe. Many bursts are followed by extremely luminous optical afterglows that can serve as a sensitive probe of "dark", intervening baryonic matter in space. I will review recent progress in our understanding of interstellar medium and intergalactic matter in the distant universe based on observations of long-duration gamma-ray bursts.

Robert Wald, University of Chicago

Nonlinear gravitational phenomena associated with small scale (as compared with the Hubble radius) density inhomogeneities are prevalent throughout our universe. Could the nonlinear effects of these small scale inhomogeneities produce significant effects on the large scale dynamics that are not properly taken into account by standard FLRW models, which treat the matter distribution as homogeneous? I will describe recent work with S. Green that provides a framework within the context of general relativity that allows one to analyze this issue in a mathematically precise manner. Within this framework we prove quite generally that, provided that matter satisfies the weak energy condition (i.e. has positive energy density in all frames), the “effective gravitational stress energy” associated with small scale inhomogeneities also must satisfy the weak energy condition and must be traceless---corresponding to gravitational radiation. In particular, nonlinear effects of small scale inhomogeneities cannot be responsible for the acceleration of our universe. We also analyze cosmological perturbation theory within this framework and calculate the corrections produced by small scale inhomogeneities to the equations satisfied by long wavelength perturbations.

Asantha Cooray, University of California Irvine

The talk will summarize latest results from HerMES and H-ATLAS extragalactic surveys at 250, 350 and 500 microns with the SPIRE instrument on the Herschel Space Observatory. HerMES is the multi-tiered SPIRE instrument GTO survey covering about 70 square degrees on a variety of extragalactic fields with existing ancillary data. H-ATLAS is currently the largest open-time program in Herschel with 600 hours of observations to map 550 square degrees. I will discuss a newly discovered population of lensed sub-mm galaxies, the halo properties of bright and faint sub-mm galaxies as revealed by clustering and fluctuation studies, evolution of dust and molecular properties, the role of sub-mm sources in galaxy formation and evolution models, sub-mm source follow-up effort, and the future of sub-mm astronomy. I will also summarize the scientific goals of the Herschel-SPIRE Legacy Survey, a program now under discussions with ESA to cover 1500 sq. degrees with SPIRE in a fast-scan mode with the ultimate goal of recovering a catalog of 1.5 million bright sub-mm sources for future studies with ALMA, CCAT, and SPICA.

Jason Tumlinson, Space Telescope Science Institute

In recent years we have come to appreciate the great importance of the gas just outside galaxies - the circumgalactic medium - to galaxy formation and evolution. I will survey the intellectual history of this subject going back to the 1960s before presenting the latest results from two large HST projects that are using the new Cosmic Origins Spectrograph to systemically characterize the gaseous halos of low-redshift galaxies. COS has uncovered a clear link between star formation and hot gas in gaseous halos beyond 100 kpc, and strong indications of winds propagating from star-forming galaxies. These results show that the circumgalactic medium likely does participate in the ongoing star formation and evolution of modern galaxies.

Andy Albrecht, University of California, Davis

Cosmic inflation has given us a remarkably successful cosmological phenomenology. But the original goal of explaining why the cosmos is *likely* to take the form we observe has proven very difficult to realize. I first review the popular idea of "eternal inflation" with an eye on the roles various infinities have (both helpful and unhelpful) in our current understanding. I then discuss attempts to construct an alternative cosmological framework that is truly finite using ideas about equilibrium and dark energy. I report some recent results that point to observable signatures.

August Evrard, University of MIchigan

In this talk, I will present galaxy clusters as systems spanning multiple spaces: the traditional crossroads of astrophysics and cosmology as well as the fast developing crossroads of theory, computation and observation. While the current paradigm for large-scale structure formation - a hierarchical web of quasi-equilibrium halos emerging from a noise field imposed by inflation - is largely secure, important details ranging from the profound (nature of dark energy) to the practical (rate of star formation as a function of galactic environment) remain poorly understood. Clusters of galaxies present opportunities for detailed testing of cosmological and astrophysical models, and I will discuss challenges posed by survey selection and cluster characterization. What's clear is that precise analysis of the cluster population requires that theory/computation meet observation on a common ground. The angle-wavelength space of the sky offers a natural crossroads for such a meeting, and this choice imposes new requirements on the community to build an efficient "cosmic sky machine". I will sketch ideas for developing community-wide cyberinfrastructure that could accelerate the pace of understanding cosmic structure formation.

Mariska Kriek, Center for Astrophysics, Harvard

At first glance the galaxy population today and even more so at earlier times exhibits a huge diversity. However, the well-known correlations between different galaxy properties, such as spatial structure, stellar population, stellar mass, stellar dynamics, and environment suggest that galaxy formation is actually an orderly process. With the recent large photometric and spectroscopic surveys and new instrumentation on the Hubble Space Telescope, it is now finally possible to study galaxies in a systematic way at earlier times, so that we can see directly how these relations change over cosmic time and what the physical processes are that drive them. Until very recently, these studies were hampered by the small sizes of spectroscopic galaxy samples, whereas much larger photometric samples lack the required spectroscopic information. I will discuss a novel approach, that makes use of medium-band photometry to perform detailed spectroscopic studies of ~3500 galaxies at 0.5