Talks & Events
KICP Colloquia: 2002
Radiative Feedback from Galaxy Formation: the fate of the first galaxies
Massimo Ricotti, University of Colorado
The theory of galaxy formation predicts that the creation process is hierarchical: small objects form first, and large galaxies form later from mergers of smaller subunits. The first galaxies are believed to have formed 100 million years after the Big Bang, at redshift $z sim 30$. In these primordial galaxies, the first stars emitted light into a previously dark universe and should have influenced the subsequent evolution of the universe in a still uncertain way. I present recent theoretical results on the formation and the evolution of the first (Population III) galaxies and effects of their self-regulating radiating feedback on the efficiency of star formation and reionization of the Universe.
Reionization and Metal Enrichment of the High-Redshift Intergalactic Medium by the First Stars
Aparna Venkatesan, CASA University of Colorado
The epoch, formation sites and effects of the first stars in the universe are some of cosmology's most intriguing yet unresolved questions today. Observations of the most distant quasars and galaxies to date imply that hydrogen reionization of the intergalactic medium (IGM) has occurred by redshifts of about 6. Radiation from the first stars is increasingly believed to have had a significant, if not the dominant, role in reionization, because of the mounting data on the decrease in the space density of bright quasars beyond redshifts of about 3. Early generations of stars are expected to be metal-free in composition, and to have signficantly harder ionizing spectra and evolutionary properties relative to their finite-metallicity counterparts. Here, I will present ongoing theoretical work that evaluates the effects of the first stars on the hydrogen and helium reionization, as well as the metal enrichment, of the high-redshift IGM. I will also discuss whether these signatures consistently reflect the same population of stars.
Bounding the mass of the graviton and other topics in Gravitational Wave Phenomenology
Lee Samuel Finn, Penn State
Dark matter in normal galaxies
Anatoly Klypin, New Mexico State University
Standard cosmological models, while very successful on large scales, face mounting problems on small scales. The models, for example, predict hundreds of dark matter subhalos inside of our Galaxy. Inner parts of rotation curves of dwarfs are not compatible with the theory. Yet, even more dramatic problem may be lurking on larger scales of normal Milky-Way type galaxies. I will discuss the situation on the amount of the dark matter in normal galaxies on scales from 10 parsec to 100 kpc, focusing on such issues as mass modeling of the Milky Way and M31 galaxies, rotation and existence of bars, microlensing counts.
Puzzling Cosmic Rays at the Highest Energies
Angela Olinto, University of Chicago
MHD Turbulence: Scaling, Anisotropy, New Regimes
Alex Lazarian, University of Wisconsin
The Pervasive Influence of Massive Black Holes in the Centers of Galaxies
Douglas Richstone, University of Michigan
The distribution of thermal pressures in the Neutral Interstellar Medium
MHD Turbulence: Scaling, Anisotropy, New Regimes
Alex Lazarian, University of Wisconsin
LISA: Listening to Gravitational Waves from Space
The LISA gravitational wave space observatory is a joint mission between NASA and ESA, scheduled to launch in 2011. It will open up the low-frequency gravitational wave window, observing supermassive black holes in distant galaxies and binary star systems in the Milky Way. Its goals include probing the earliest phases of galaxy formation, testing general relativity and the no-hair theorem for black holes, positively identifying black holes, and possibly even measuring the acceleration history of the universe to high redshift. Unlike ground-based detectors, it will make observations of such sensitivity that it will be limited more by backgrounds of gravitational waves produced by distant sources than by instrumental noise. LISA technology presents challenges that have not been met in space before the critical components will be tested in space in 2006. The talk will cover all aspects of LISA's design concept and scientific mission.
Black Holes: Demographics and Galaxy Evolution
David Merritt, Rutgers University
CMB Anisotropy: Status and Prospects
Lyman Page, Princeton University
Plasma Turbulence in the Solar Wind and in the Galaxy
Stephen Spangler, University of Iowa
Looking Beyond the Big Bang
Paul Steinhardt, Princeton University
The conventional picture of cosmic evolution, a combination of the big bang model and the inflationary scenario, assumes that the big bang is the beginning of space time. This talk will discuss a radical alternative, the "cyclic universe," based on the concept of an eternal universe with an endless sequence of expansions and contractions. We will discuss how the problems of earlier cyclic models can be avoided and how all of the successful predictions of the conventional picture can be reproducedby events before the big bang without having a period of inflation.
Analysis Issues for CMB Anisotropies
Ben Wandelt, University of Illinois
Principles of Electricity and Magnetism with Applications to Quasars, Pulsars, and Gamma Ray Bursts
Roger Blandford, CalTech
Ultra-High Energy Cosmic Rays in a Structured and Magnetized Cosmic Environment
Gunter Sigl, GReCO, IAP
We discuss recent results based on simulations of ultra-high energy cosmic ray propagation in the Local Supercluster with magnetic fields reaching fractions of a micro Gauss in galaxy filaments and clusters, as suggested by several arguments. It is shown that scenarios involving a small number of sources around 10 can be consistent with all observations including the newest HiRes data. Since in such scenarios the contribution of sources at cosmological distances to the observed flux is in general negligible, the observation of a GZK cutoff is not necessarily associated with cosmological sources as often claimed.
The Pierre Auger Observatories: Why and How
Jim Cronin, University of Chicago
I will give a very personal view of how the project came about. As in the Japanese tale "Roshomon" my view may be different from others but it is an honest one. Auger has been nearly eleven years in the making and will require about three more to complete. What I thought was an obvious thing to do took many years to convince others. I will describe briefly the features of the design and show some of the beautiful events from the large scale prototype which is now running. The talk will be a prelude to the mini-symposium that will be held on Friday afternoon.
Cosmological constraints from evolution of X-ray clusters at z=0.5
Alexey Vikhlinin, Smithsonian Astrophysics Observatory
Evolution of the mass function of clusters of galaxies is a sensitive measure of the cosmological parameters, especially Omega. I will discuss some recent results on cluster evolution from the CfA-IfA-ROSAT survey (160 deg2) which found more than 40 X-ray bright clusters at z>0.4. I will discuss how to use the cluster baryon masses as a proxy for the total mass function and argue that this is a better approach than using temperatures or X-ray luminosities. An application of this method to the 160 deg2 sample indicates a strong evolution of the cluster mass function since z=0.5. The observed evolution defines a narrow band in the Omega-Lambda plane which intersects with the cosmological constraints from CMB and SNIa near Omega=0.3 and Lambda=0.7.
Small-Scale Structure in Lens Galaxies
Charles Keeton, University of Chicago
Strong gravitational lensing offers two unique tests of small-scale structure in distant galaxies. First, lens theory predicts that each lens should have a faint image near the center of the lens galaxy. These "core" images provide the only direct probe of the mass profile in the inner 100 pc of distant galaxies. The fact that core images have not been observed, even in radio lenses, places lower limits on the densities on these scales. Second, the flux ratios between the images in 4-image lenses provide a powerful test of the smoothness of galaxy mass distributions, which in turn tests the prediction from CDM that galaxies are lumpy. Dalal & Kochanek (2002) claimed that lensing proves the existence of substructure in amounts consistent with CDM. I will assess the state of the data and theory behind this claim, and discuss future prospects on both fronts.
First results from the DEEP2 Redshift Survey
Marc Davis, University of California, Berkeley
The DEIMOS spectrograph was delivered and successfully commissioned on the Keck-II telescope in Hawaii last Spring, and the DEEP2 Redshift survey began in July, 2002. This survey will provide high resolution spectra of ~60,000 faint galaxies over 3.5 square degrees at a median redshift z~1. To date we have successful observations from 70 out of a total of 480 masks, approximately 15% of the survey. I will review the design of the survey, the science goals, and initial, very preliminary results. In two year's time, we hope to use the measured abundance of groups and clusters within the survey volume to set a new, improved constraint on the dark energy equation of state. Some details of the survey can be found at http://deep.berkeley.edu/
A Sensitive New All Sky Survey in the Thermal Infrared
Ned Wright, UCLA
The Next Generation Sky Survey, a MidEx mission proposed for launch in late 2006, will map the the sky in four bands from 3.5 to 23 microns with sensitivities 3 to 6 orders of magnitude better than previous work. This survey should identify the closest stars to the Sun and the most luminous galaxies in the Universe.
Gravitational 3-D mass Tomography
Tony Tyson, Bell Labs, Lucent Technologies
There is evidence for vacuum energy accelerating the recent expansion of the universe. Does this "dark energy" exist? What is it's equation of state? A new and direct probe of dark energy is provided by 3-D mass tomography. Dark matter may be "seen" directly via its coherent gravitational lens warping of thousands of high redshift galaxy images. Tomographic inversion of these cosmic mirages in deep wide-field imaging surveys enables a unique 3-D mass view of our universe. Images of dark matter structures and their development over cosmic time will sharply constrain dark energy and its physical properties. These multiple weak lens probes complement those from cosmic background radiation, SZ probes, and supernovae, and thus test the consistency of our cosmology. The Deep Lens Survey, and plans for the Large Synoptic Survey Telescope will be reviewed.