26 September 2008	24 October 2008	21 November 2008
3 October 2008	31 October 2008	5 December 2008
10 October 2008	7 November 2008	12 December 2008
17 October 2008	14 November 2008

Massimo Ricotti, University of Maryland at College Park

Fossils of the first galaxies in the Local Group  

In this talk I show results of cosmological simulations suggesting a possible identification of at least some dwarf spheroidal galaxies in the Local Group as the fossils of the first galaxies ("pre-reionization fossils"). I also revisit the problem of gas accretion onto minihalos after reionization. I show that primordial minihalos with $v_{cir}<20$~km~s$^{-1}$ stop accreting gas after reionization, as it is usually assumed, but in virtue of their increasing concentration and the decreasing temperature of the intergalactic medium as redshift decreases, they may have a late phase (at redshift $z<2$) of gas accretion and possibly star formation. As a result we expect that pre-reionization fossils have a more complex star formation history than previously envisioned. The dwarf spheroidal galaxy Leo~T fits with this scenario. Another prediction of the model is the existence of a population of gas rich minihalos that never formed stars. A subset of compact high-velocity clouds may be identified as such objects but the bulk of them may still be undiscovered.

Janna J Levin, Barnard College/Columbia University

A Periodic Table for Black Hole Orbits  

We are on the verge of a truly remarkable observational possibility: the direct detection of black holes through gravitational radiation. Knowledge of the dynamics around rotating black holes is imperative to the success of gravitational wave observatories. While they have been studied extensively, a general understanding of the elaborate orbits has been elusive. We demonstrate that the entire dynamics around black holes can be understood through a beautiful, geometric taxonomy of perfectly periodic orbits. Through a correspondence to the rational numbers, we build a periodic table of black hole orbits in analogy with the chemical periodic table. A remarkable implication of this taxonomy is that the simple precessing ellipse familiar from planetary orbits is not allowed in the strong-field regime. Instead, eccentric orbits trace out precessions of multi-leaf clovers in the final stages of inspiral.

Fulai Guo, University of California, Santa Barbara

AGN Feedback Heating in Clusters of Galaxies  

AGN feedback plays a key role in suppressing cooling flows in galaxy clusters, and thus in shaping the high-luminosity end of the galaxy luminosity function. Recent Chandra observations have detected X-ray deficient bubbles in many galaxy clusters. In this talk, I will use hydrodynamic simulations to show that cosmic rays leaked from these bubbles may heat the intracluster medium, and thus efficiently suppress the cooling catastrophe. No fine-tuning of various parameters is required in our model. In the second part of my talk, I will perform the first global linear stability analysis of (AGN) feedback models. I will show that thermal instability in cool core clusters can be suppressed by the AGN feedback mechanism, provided that the feedback efficiency exceeds a critical lower limit. Furthermore, our analysis naturally shows that the clusters can exist in two distinct forms. Globally stable clusters are expected to have either: 1) cool cores stabilized by both AGN feedback and conduction, or 2) non-cool cores stabilized primarily by conduction. Intermediate central temperatures typically lead to globally unstable solutions.

Matthias Beilicke, Washington University of St.Louis

M87 - a unique laboratory to study jet physics at very high energies  

The giant radio galaxy M87 is located at a distance of ~16 Mpc and harbours a supermassive black hole in its center. The structure of the relativistic plasma jet of M87 is resolved at radio, optical and X-ray wavelengths. M87 belongs to the class of active galactic nuclei (AGN) and is the only extragalactic source not belonging to the class of blazars (plasma jet pointing towards the observer) which is detected at very high energies (E>100 GeV, i.e. VERITAS). This makes it a unique laboratory to study jet physics and the corresponding emission processes at very high energies. The current status as well as the prospects of future simultaneous multi-wavelength observations are discussed.

Douglas Spolyar, ucsc

Dark Matter and The first Stars: a new stage of stellar evolution driven by DM annihilation  

One of the outstanding problems in astrophysics is to determine the mass and properties of the first stars, as these determine the astrophysical environment of the early universe. These stars form when the universe is 200 million years old and are thought to begin the process of element enrichment necessary for the beginnings of life. They form at the very centers of million solar mass concentrations of dark matter (DM), where the DM density is exceptionally high. We propose that the first phase of stellar evolution in the history of the Universe may be Dark Stars (DS), powered by dark matter heating rather than by nuclear fusion, and in this paper we examine the early history of these DS. The power source is annihilation of Weakly Interacting Massive Particles (WIMPs) which are their own antiparticles. These WIMPs are the best motivated DM candidates and may be discovered by GLAST or at the Large Hadron Collider at CERN, which have just started taking data. We build up the dark stars from the time DM heating becomes the dominant power source, accreting more and more matter onto them. We have included many new effects in the current study, including a variety of particle masses, accretion rates, energy transport mechanisms, nuclear burning, feedback mechanisms, and possible repopulation of DM density due to capture. Remarkably, we find, that in all these cases, we obtain the same result: the first stars are very large, 500-1000 times as massive as the Sun, and cool (Tsurf < 10, 000K) during the accretion. These result differs markedly from the standard picture in the absence of DM heating, in which the maximum mass is about 140 M⊙ (Tan and McKee) and the temperatures are much hotter (Tsurf > 50, 000K). DS lead to element enrichment that provides a better match to data, and eventually collapse to form massive black holes that may provide seeds for the otherwise unexplained supermassive black holes observed at early times as well as intermediate black holes.

Sudeep Das, Princeton University

CMB Lensing: A tool for Cosmology and Astrophysics  

Large scale structure in the universe deflects cosmic microwave background (CMB) photons by roughly 3 arcminutes. This deflection field reflects the history of cosmological expansion and growth of structure. With high resolution ground based CMB experiments like the South Pole Telescope and the Atacama Cosmology Telescope already underway, and the space based Planck satellite nearing its launch, time is ripe for perfecting a new set of tools and ideas to reap the scientific benefits of this exciting effect. I will describe high resolution simulations, new analysis techniques and theoretical expectations for an array of possible projects involving CMB lensing and large scale structure surveys which will shed new light on dark energy, dark matter and galaxy formation.

Joel R Primack, University of California - Santa Cruz

Recent work on galaxy mergers and the formation of spheroids  

Mergers of gas-rich spiral galaxies can make rotating elliptical galaxies that have kinematics much like those from the SAURON observations, and recent work led by my just-finished PhD student Matt Covington shows that their properties look very much like those seen at redshifts up to z~3. However, large elliptical galaxies are often round on the sky and non-rotating, and these are not formed by binary mergers. However, at high redshifts z>2 the merger timescale is comparable to the Hubble time so mergers typically overlap. High-resolution simulations by my just-finished PhD student Greg Novak appear to produce massive elliptical galaxies like those observed.

Matthew McQuinn, Harvard

HeII Reionization and Its Effect on the IGM  

Observations of the intergalactic medium (IGM) suggest that quasars reionize the HeII at z ~ 3. HeII reionization heats the IGM by tens of thousands of Kelvin, and it affects the statistics of the HI and HeII Lyman-alpha forests. I will present a set of simulations of HeII being reionized by quasars. These simulations lead to a different picture for this process than in previous studies. If quasars have a mean spectral index of 1.5, I find that HeII reionization heats regions in the IGM by as much as 30,000 K above the temperature that is expected otherwise, with the volume-averaged temperature increasing by ~10,000 K and with large temperature fluctuations on ~50 comoving Mpc scales. However, the amount of heating can be much larger if the spectrum is harder. I discuss how temperature fluctuations from HeII reionization bias measurements from the HI Lyman-alpha forest of the IGM temperature and of cosmological parameters, and I quantify the detectability of these fluctuations with wavelet statistics. I conclude by contrasting the morphology of HeII reionization by quasars with that of hydrogen reionization by stars.

Laurie D Shaw, McGill University

Cluster Mass Estimation via the Sunyaev-Zel'dovich Effect  

Measuring the redshift evolution of the cluster mass function provides us with a sensitive means of constraining cosmological parameters. Sunyaev-Zel'dovich Effect experiments aim to survey a large fraction of the sky searching for clusters via their imprint on the CMB. However, to probe the growth of structure it is vitally important that we can accurately infer the mass of clusters via measurements of their integrated SZ flux. In this talk I will present a detailed analysis of the slope, normalisation and intrinsic scatter in the SZE flux - mass scaling relation via simulated cluster samples. Using synthetic sky-maps constructed from a high-resolution cosmological 'lightcone' simulation, I will evaluate the accuracy with which cluster size and flux can be measured in practice, and discuss the characteristics of the detected cluster catalogues. Finally I will discuss the potential for improved cluster catalogues by cross-matching with optical data.

Fabian Schmidt, The University of Chicago

Structure Formation in Modified Gravity: The Non-Linear Regime  

Instead of adding another dark component to the energy budget of the Universe in trying to explain the accelerated expansion, one can ask whether the cause is in fact the behavior of gravity itself on the largest scales. In this talk, I will consider a sub-class of so-called f(R) gravity theories which closely follow the LambdaCDM expansion history, while at the same time evading tight Solar System constraints on gravity. I will present new results from cosmological N-body simulations which consistently solve for the modified gravitational force. In particular, I will discuss the effects of modified gravity on structure formation, dark matter halo properties, and cosmological observables.

Wenjuan Fang, Physics Department, Columbia University

Gravitational leakage vs cosmological constant  

The accelerated expansion of the universe at the present time may be caused by a different law of gravity from General Relativity on cosmological scales instead of by a missing dark energy component. A leading example is the Dvali-Gabadadze-Porrati (DGP) self-accelerating braneworld model where cosmic acceleration arises from graviational
leakage into an extra dimention. I will show the results of a Markov Chain Monte Carlo study of this model given the current observations of the cosmic microwave background anisotropies from the 5-year WMAP, supernovae from the SNLS and
Hubble constant from the HST key project, and discuss how it is compared to the successful Lamda-CDM model that is based on General Relativity but with a cosmological constant.

8 October 2008	5 November 2008	3 December 2008
22 October 2008	19 November 2008

Craig Hogan, The University of Chicago

Indeterminacy of Holographic Quantum Geometry  

Theoretical motivations will be reviewed for the idea that spacetime is holographic: there is a minimum time or length in nature, and the third dimension of space emerges in quantum theory from time evolution, in the normal direction to a light sheet. A new phenomenon will be described that arises in such holographic geometry: "holographic noise", caused by an indeterminacy of transverse position. It will be shown that currently operating interferometric gravitational-wave detectors have the capability to detect holographic noise. These experiments provide a zero-parameter test of the holographic hypothesis. In a holographic world, they provide a direct, precise measurement of the fundamental minimum interval of time.

Marcelo Gleiser, Dartmouth College

The Chirality of Life: From Phase Transitions to Astrobiology  

Life is chiral. Amino acids that make up biomolecules are left-handed, while all sugars are right-handed. And yet, when synthesized in the laboratory, the solutions come out 50-50. Is life's chirality simply an accident, or is it the result of dynamical processes that occurred in early Earth, during prebiotic times? If life exists elsewhere in the Universe, will it choose the same chirality? In this talk, I will address these and other questions of interest in astrobiology, using techniques from nonequilibrium statistical mechanics and field theory. In particular, I will argue that life's chirality might be due to a symmetry-breaking phase transition. Exploring this possibility, I will obtain bounds on possible processes that may have selected life's chirality here and possibly in other life-bearing planetary platforms. Coupling the polymerization reactions to a simple model of the early-Earth environment, we conclude that Earth's chirality was selected randomly. A large sample of planetary platforms with stereochemistry will have a 50-50 chiral distribution.

Eanna Flanagan, Cornell University

Cosmological Inhomogeneities and Dark Energy  

The issue of whether the backreaction of inhomogeneities can mimic the effects of dark energy has been a subject of much debate. I review the evidence on both sides of this issue and discuss what needs to be done to resolve it. I also discuss the extent to which inhomogeneities perturb high precision measurements of dark energy.

Julie McEnery, NASA/GSFC

Early results from the Fermi gamma-ray space telescope  

The Fermi Gamma-ray Space Telescope, recently launched in June 2008, is a satellite based observatory to study the high energy gamma-ray sky. There are two instruments on Fermi: the Large Area Telescope (LAT) which provides coverage from 20 MeV to over 300 GeV, and the Gamma-ray Burst Monitor (GBM) which provides observations of transients from 8 keV to 30 MeV. Since its launch, Fermi has detected over one hundred gamma-ray bursts (three above 100 MeV), dozens of flaring AGN, a couple of Galactic transients, radio-loud and radio-quiet pulsars, and is enabling a detailed study of the many other persistent sources in the high energy gamma-ray sky. In this talk, I will review the early results from Fermi, and discuss the current status and future plans for the observatory.

Alison Coil, University of California, San Diego

Clustering, Quenching, and Feedback: Galaxies and AGN at z=1  

Roughly half of the red elliptical galaxies observed today have formed since z=1. I will present galaxy clustering results from the DEEP2 Redshift Survey that strongly constrain the mechanism responsible for the quenching or cessation of star formation in these galaxies. I will show where this quenching is occurring on large scales and how it can not be due primarily to cluster-specific physics. I will also present results on the clustering of optically-bright quasars and X-ray selected AGN and show how AGN accretion correlates with the star formation activity in galaxies at z=1. I will also show new results on the prevalence of outflowing galactic winds at z=1 and discuss their role in quenching star formation. Finally, I will present a new wide-area prism survey that will allow further studies of galaxy evolution to z=1 with the largest faint galaxy survey to date.

1 October 2008	29 October 2008	26 November 2008
15 October 2008	12 November 2008

Wendy Freedman, Carnegie Observatories

New Measurements of the Hubble Constant and Dark Energy  

James Annis, Fermilab

The Dark Energy Survey  

The Dark Energy Survey is a 5000 sq degree imaging survey of the South Galactic cap starting in 2011. It aims to make a photometric redshift galaxy map of the area that will be used in cluster counting, baryon acoustic oscillation, and weak lensing measurements of cosmology and dark energy, in conjunction with a supernova time domain survey. This talk will describe the DES, its status, and parts of the underlying cluster counting work.

Robert D. Gehrz, University of Minnesota

The Stratospheric Observatory for Infrared Astronomy (SOFIA)  

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a joint U.S./German Project to develop and operate a 2.5-meter infrared airborne telescope in a Boeing 747-SP that flies in the stratosphere at altitudes as high as 45,000 and is capable of observations from 0.3um to 1.6mm with an average transmission greater than 80 percent. SOFIA will be staged out of the NASA Dryden Flight Research Center aircraft operations facility at Palmdale, CA and the SOFIA Science Mission Operations Center (SSMOC) will be located at NASA Ames Research Center, Moffet Field, CA. First science flights will begin in 2009, the next instrument call and the first General Observer science call will be in 2010, and a full operations schedule of about 120 8 to 10 hour flights per year will begin in by 2014. The observatory is expected to operate for more than 20 years. SOFIA will initially fly with nine focal plane instruments that include broadband imagers, moderate resolution spectrographs that will resolve broad features due to dust and large molecules, and high resolution spectrometers capable of studying the kinematics of molecular and atomic gas lines at km/s resolution. We describe the SOFIA facility and outline the opportunities for observations by the general scientific community, future instrumentation developments, and operations collaborations. The operational characteristics of the SOFIA first-generation instruments are summarized and we give several specific examples of the types of scientific studies to which these instruments are expected to make fundamental scientific contributions.

John Carlstrom, University of Chicago

The SZA, CARMA and the South Pole Telescope: New results and future plans  

Mazeh Tsevi

Transiting extra-solar planets: how do we find them and what can we learn from them  

More than 300 extrasolar planets were discovered since 1995, when the first planet was detected. About 50 of these planets eclipse their parent star once every orbital period. The detection of these transiting planets allowed in the last few years the derivation of the planetary dynamical masses and radii and sometimes even the planetary temperatures and atmospherical features. The transiting timing can be quite accurate, and therefore small deviations from the planetary Keplerian motion can also be detected. The talk will review the detection and study of the presently known transiting planets.

8 December 2008

Daniel Holz, Los Alamos National Laboratory

Cosmology from Gravitational-Wave Standard Sirens  

We discuss the use of gravitational wave sources as probes of cosmology. The inspiral and merger of a binary system, such as a pair of black holes or neutron stars, is extraordinarily bright in gravitational waves. By observing such systems it is possible to directly measure a self-calibrated absolute distance to these sources out to very high redshift. When coupled with independent (electromagnetic) measures of the redshift, these "standard sirens" enable precision estimates of cosmological parameters. We review potential GW standard sirens for the LIGO and LISA gravitational wave observatories, including gamma-ray bursts and supermassive black-hole inspirals. Percent-level measurements of the Hubble constant and the dark energy equation-of-state may be feasible with these instruments.

2 December 2008

9 December 2008

Douglas G MacMynowski, Caltech

Thirty Meter Telescope: Design, Performance, and Control  

The Thirty Meter Telescope (TMT) will provide a significant increase in scientific capability over the current generation of 8-10m optical telescopes when it is complete. Stringent performance targets for both seeing-limited and adaptive-optics modes of operation are both required, and enabled, by advances in performance modeling and control. I will give an overview of the telescope design, the current performance estimates for the telescope, and the modeling tools used to analyze performance. I will give more detail on my own area of expertise: the modeling and control of dynamic disturbances; principally unsteady wind loads due to turbulence inside the enclosure. Wind loads are relevant both on the telescope top end and supporting structure, and over the primary mirror. The former is managed through careful enclosure design, and the elevation axis mount control system. Wind loads on the 492-segment primary mirror (M1) are controlled by the 1476 segment actuators with feedback from edge sensors.

Michael Brown, Cambridge University

The CLOVER Experiment  

I will describe the objectives, design and current status of CLOVER, an upcoming ground-based experiment, operating at 97, 150 and 225 GHz, aimed at measuring the faint B-mode polarisation pattern in the cosmic microwave background. Assuming CLOVER meets its performance goals and that systematics and foregrounds can be controlled, CLOVER should make a strong measurement of the B-mode signal due to gravitational lensing and should detect the B-mode signal due to primordial gravitational waves if the tensor-to-scalar ratio, r is > 0.03. CLOVER observations are expected to begin from the Atacama Desert in Chile in late 2009 or early 2010.