Upcoming and Previous Seminars

Note that if the talk's pdf or ppt is available after the talk, you can get it by clicking on the talk title.

Physics/Astronomy C290C Cosmology Seminar 2006-2007
The Physics/Astronomy C290C series consists of the LBNL-Physics-Astronomy Cosmology seminars held Tuesdays 1:10-2:00 pm in room 544 Campbell Hall (also videoconferenced to LBL 50A-5131). Feel free bring your lunch.
Please contact Joanne Cohn to add to this list or to suggest speakers.

Note that there are also other talks which generally might be of interest, including Cosmology Workshops and:

2006-2007 Seminars: ( Previous Years)

May 2007:
May 1, Tuesday 1:10 pm
Pat McDonald, CITA
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Toward precision cosmology from the theory side: renormalizing large-scale structure perturbation theory"
Statistics of the large-scale density fluctuations in the Universe provide an invaluable source of information on the very early Universe, where the initial density perturbations that grow by gravitational instability were created, and on the material content and gravitational laws of the Universe, which determine the growth of structure and how it looks to us from a distance. Giant surveys, ongoing and planned, are dramatically increasing the precision of our measurements of the clustering of galaxies and other tracers of large-scale structure. To fully exploit these surveys it is necessary to improve our theoretical computations of the observables. I discuss some of my recent work using perturbation theory to compute large-scale clustering. Baryonic acoustic oscillation (BAO) surveys aimed at probing dark energy, in particular, fall in the range of scales where perturbation theory should be most useful. Interesting renormalization issues arise in these computations. Time permitting, I may discuss the possibility of measuring the BAO scale at z~2.5 using the Lyman-alpha forest.

May 3, Thursday 4:00 pm (RPM)
Pat McDonald, CITA
LBL 50A-5132
"Probing inflation, dark matter, dark energy, etc. using the Lyman-alpha forest"
Cosmologists work to answer some of the oldest questions of humanity: How did the Universe begin? What is it made of? What rules does it follow? Observations of the large-scale structure of the Universe address these questions in several ways: Measurements of the scale dependence of density fluctuations tell us about the initial conditions for structure formation, set in the very early Universe. Measurements of the expansion and growth of structure with time tell us about the matter content and gravitational laws. I will mostly discuss one large-scale structure probe: the Lyman-alpha forest (LyaF) - the absorption in high redshift quasar spectra by neutral hydrogen in the intergalactic medium. The LyaF provides a good probe of the density field at z~3 on scales down to ~100 kpc. When combined with the CMB on larger scales, the LyaF observed in thousands of quasar spectra from the Sloan Digital Sky Survey currently provides the best constraints on the power spectrum of initial density perturbations, neutrino masses that affect structure formation, and warm dark matter. These constraints should improve significantly in the near future. I will also discuss the possibility of probing dark energy by using a future large survey to detect baryonic acoustic oscillations in the LyaF.
May 3, Thursday 4:10 pm (Astronomy Colloquium)
David Schlegel, LBL
1 Le Conte Hall
"State of the Art and Future of Baryon Acoustic Oscillations"

May 7 Monday 4:30 pm (Physics Colloquium)
John Mather, NASA
1 LeConte Hall
"From The Big Bang To COBE , The Nobel Prize, And James Webb Space Telescope"

May 11 Friday all day (Davis)
CINC '07
May 17, Thursday 4:00 pm (RPM)
Craig Hogan, U Washington
LBL 50A-5132
"New Astrophysics and Physics with LISA"
A brief overview will be presented of the design parameters, capabilities and main science goals of the proposed Laser Interferometer Space Antenna. Several areas will be highlighted in some more detail, such as the potential and limitations of black hole binary waveforms as distance estimators for precision cosmology, and detection of gravitational wave backgrounds due to cosmic superstrings. Finally, a newly conjectured quantum-gravity effect will be described: holographic uncertainty,'' a fundamental quantum indeterminacy of eigenstates of transverse position or angle that may be observable with LISA or with suitably designed ground based interferometers.

May 18, Friday 12:00 pm (INPA seminar)
Eddie Baron , Oklahoma
LBL 50-5026
"SNe Ia Nodels and Observations: A Spectroscopist's Point of View "
I briefly describe the state of empirical determinations of the effectiveness of the use of SNe Ia for cosmology, SNe Ia progenitors, and numerical modeling of the SNe Ia explosion mechanism. From there I describe the status of spectral modeling of SNe Ia and present preliminary results on building a physical "template" that matches observations and can be used to study variations in the explosion mechanism, progenitor age, and composition.
May 22, Tuesday 1:10 pm
Yue Shen, Princeton
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
" Clustering of high-redshift (z>2.9) quasars and implications for quasar environments"
We have measured the clustering of high redshift (z>2.9) quasars from SDSS DR5. These high redshift quasars cluster much more strongly than their low-redshift counterparts, indicating they live in very massive, highly biased dark matter halos. Combining the clustering properties and quasar luminosity function, the quasar lifetimes (or duty cycles) are broadly constrained.

April 2007:
Apr. 3 Tuesday 1:10 pm
Stelios Kazantzidis, KIPAC/Stanford
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Infalling Satellites and Structure of Galactic Disks in CDM Models" [note 109 Mb file]
The Cold Dark Matter (CDM) model of hierarchical structure formation has emerged as the dominant paradigm in galaxy formation theory owing to its remarkable ability to explain a plethora of observations on large scales. Yet, on galactic and sub-galactic scales the CDM model has been neither convincingly verified nor disproved, and several outstanding issues remain unresolved. Using a set of high-resolution numerical simulations I investigate whether the abundance of substructure predicted by CDM models is in conflict with the existence of thin, dynamically fragile galactic stellar disks. I show that encounters of massive subhalos with the center of the host potential where the disk resides at z < 1 are quite common and yield significant damage to the disk. However, these violent interactions are not absolutely ruinous to the survival of disks. I demonstrate that infalling satellites produce several distinct observational signatures including flaring, long-lived, low-surface, ring-like and filamentary structures, and a complex vertical morphology that resembles the commonly adopted thin-thick disk profiles used in the analysis of disk galaxies. These results imply that substructure plays a significant role in setting the structure of disks. Upcoming galactic surveys and astrometric satellites offer a unique opportunity to distinguish between competing cosmological models and constrain the nature of dark matter on non-linear scales through detailed observations of galactic structure.

Apr. 5, Thursday 12:00 pm (INPA seminar)
Zeljko Ivazic , Washington
LBL 50-5026
"Reaching for the sky with SDSS and LSST"
Despite a several thousand years long history, sky surveying is experiencing a bonanza as detectors, telescopes and computers become ever more powerful. I will discuss how the unprecedentedly accurate and diverse data from the optical Sloan Digital Sky Survey have recently enabled numerous exciting discoveries. I will use three specific examples (asteroids, quasar variability, and mapping of the Milky Way stellar distribution in a 7-dimensional phase space spanned by the position and velocity vectors, and metallicity), to give a preview of what to expect from the upcoming next-generation surveys, such as the Large Synoptic Survey Telescope.

Apr. 9 Monday 4:30 pm (Physics Colloquium)
Lawrence Krauss, Case Western Reserve University
1 LeConte Hall
"Further Reflections On The Dismal Future Of The Universe "
Some years ago I argued that life must end in an eternally expanding universe. That was the good news. In a universe dominated by a cosmological constant things are as bad as they can possibly be. During this lecture I will discuss the future of computation and information processing, the future of galaxies and large scale structure, the future of observational cosmology, and finally, the future of matter. Until the latter is considered, the news is all bad. However, I will end on a bright note: Even if protons ultimately decay, diamonds will be forever.
Apr. 10 Tuesday 1:10 pm
Bhuvnesh Jain, U Penn
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Designing surveys to test dark energy/modified gravity: examples from weak lensing"
Apr. 16, Monday 12:10 pm (TAC seminar)
Bill Forman, CfA
544 Campbell Hall
"Shocks, Bubbles, and Filaments: the Effects of Supermassive Black Hole Outbursts in Galaxies, Groups, and Clusters"

Apr. 17 Tuesday 1:10 pm
Oleg Gnedin, U. Michigan
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Constraints on the dark matter halos of disk galaxies from the Tully-Fisher relation"
Disk galaxies obey a tight correlation between luminosity and rotation speed, known as the Tully-Fisher relation. The slope, intercept, and scatter of this relation provide critical constraints on galaxy formation models. I will describe a new modeling approach of a well-defined sample of 81 disk-dominated galaxies from the SDSS redshift survey and the resulting constraints on the stellar-to-total mass fraction and the angular momentum parameter. The best-fit models with a standard stellar IMF overproduce the galaxy stellar mass function and predict the dynamical mass-to-light ratios systematically lower than those inferred from galaxy-galaxy weak lensing and satellite dynamics. I will present three possible solutions to these problems, which for the first time may relieve the observational tension between the TF relation and the galaxy stellar mass function.

Apr. 24 Tuesday 1:10 pm
Ivelina Momcheva, Arizona
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Environments of Strong Gravitational Lenses"
The number of known strong galaxy-size gravitational lenses is increasing, as is the precision of measurements of lens properties, potentially allowing lensing to become a competitive tool for studying cosmology and the structure of galaxies. However, neglecting the environments of lenses creates biases and uncertainties in lensing results that limit their usefulness. I will start by discussing the effects of lens galaxy environments and other structures superimposed along the line-of-sight. I will then describe our observational survey, which addresses the problem, show results from it, and discuss the applications of these results to lens knowledge. Finally, I will describe how we are turning the problem around and using the poor groups of galaxies that we have discovered around lenses to study the evolution of group galaxies since z~0.6.

Apr 30, Monday 3:10 pm
Alyson Brooks , U Washington
544 Campbell Hall (RAL Seminar)
"The Evolution of Disk Galaxies Over Cosmic Ages"
I will present the latest results from our set cosmological N-body simulations that form individual spiral galaxies. Our dramatically increased resolution and physically motivated prescription for supernovae feedback allows us to overcome long-standing problems with past CDM disk galaxy simulations. We form galaxies that 1) have a realistic angular moment content with scale lengths and light profiles similar to observed galaxies, 2) a reasonable number of satellite galaxies when compared to observations, and 3) reproduce the observed rend of "downsizing". These galaxies also reproduce the observed mass-metallicity relation for galaxies. I will show in detail that our mass-metallicity trend is the result of star formation efficiency decreasing with decreasing galaxy mass. This trend in star formation efficiency is also capable of explaining observed chemical trends in stellar halos (such as in our own Milky Way) and surviving dwarf satellites.

Apr 30 Monday 4:30 pm (Physics Colloquium)
Saul Perlmutter, UCB and LBL
1 LeConte Hall
"An Observationalist Take on Dark Energy: the Return of the Optimists"
I present a springtime antidote to recent doom-and-gloom theoretical prognoses for the fate of life and doubts of future scientific understanding in an accelerating universe. From the observationalists' perspective, the exciting new challenge of studying dark energy -- or its alternatives -- has sparked the development of new measurement techniques and analyses, some that are now beginning to give results, and some just now beginning to be attempted. The expected flood of new, precise cosmological data is precisely what might be expected to trigger a new generation of theoretical ideas and advances. So, while these are clearly multi-year (some decade-long) efforts, the reports of the "death of science" appear exaggerated. I will describe recent results and the steps forward for the existing supernova technique (both on the ground and in space with HST and then SNAP), and their combination with the new non-supernova methods, weak lensing and baryon oscillations, that together can make this springtime optimism realistic.

March 2007:

Mar. 5 Monday 4:30 pm (Physics Colloquium)
Katie Freese, U Michigan and Berkeley
1 LeConte Hall
"Inflationary Cosmology: from Theory to Observation and Back "
The idea of "inflationary" expansion of the very early universe was proposed twenty five years ago to resolve cosmological problems of the Hot Big Bang. Inflation blows up small regions of the universe to the point where they are large enough to explain how the universe can be so homogeneous on large scales and can reach an age of fifteen billion years. These models also predict the production of density perturbations that lead to galaxy formation and, as a by-product, leave imprints in the cosmic microwave background. These imprints provide stringent tests of inflation. Data from the Wilkinson Microwave Anisotropy Probe provide confirmation of the basic predictions of inflation, and are allowing cosmologists to begin to differentiate between individual models. This talk will review the basic principles of inflationary models and discuss the current situation of comparison with data.
Mar. 5 5:30 pm
George Smoot, UC Berkeley
Berkeley Repertory Theater
"The Big Bang, Cobe, And The Relic Radiation Traces Of Creation"
Mar. 6 Tuesday 1:10 pm
Marcelo Alvarez, KIPAC/Stanford
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Modeling Reionization and its Observational Consequences"
Reionization separates the cosmic dark ages from the epoch of galaxy formation and evolution, defining the current frontier of the highest redshift observations. I will discuss recent progress in its numerical and analytical modeling, with a focus on the relationship between the large scale structure of matter and the size and topology of HII regions. In particular, I will present results of combined N-body/radiative transfer simulations of the progress of reionization on 100 Mpc scales, and how they compare to analytical models for the characteristic scales of reionization. Different reionization scenarios, such as the role of radiative feedback and the ionizing efficiency of collapsed matter, lead to differing morphologies and scales in reionization. I will describe how these theoretical models can be applied to observations of the fluctuating 21 cm background, secondary anisotropies in the CMB, and high-redshift galaxies and quasars. Correlations between these different observational probes will reveal not just the reionization history, but also the connections between its morphology and that of early structure formation.

Mar. 13 Tuesday 1:10 pm
Adam Lidz, Harvard-Smithsonian CfA
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Probing Hydrogen Reionization"
Detailed observations of the Epoch of Reionization (EoR) will characterize the nature of the first luminous sources in the universe, describe their impact on the surrounding IGM, and fill in a significant gap in our understanding of the history of the universe. I will describe recent efforts to theoretically model the EoR. Then I will discuss the theoretical interpretation of quasar absorption spectra at z~6, and comment on future 21 cm probes of reionization.
Mar. 13 Tuesday 7:30 pm (Physics Oppenheimer Lecture)
Stephen Hawking, Cambridge
Zellerbach Hall (sold out)
"Strictly Speaking"

Mar. 16, Friday 12:00 pm (INPA seminar)
Lifan Wang, Texas A&M University
LBL 50-5026
From Polarized SNe and the expansion of the Local Universe
I will discuss recent results from our efforts to probe in great detail the geometric structure of SNIa, and to apply SNIa as cosmological probes using the CMAGIC method. Spectropolarimetry of Type Ia supernovae (SNIa) show that the degree of polarization of SNIa is typically below 0.3% in the continuum but can be as large as 1-2% across some strong P-Cygni lines. The degree of polarization across the Si II 635.5 nm is found to be correlated to the brightness of the Type Ia supernovae. The polarization data reveals a geometric structure in which the center of the SN ejecta are typically spherically symmetric but with layers above about 10,000 km/sec highly aspherical. The asphericity at the outer, high velocity layers can not be explained by a smooth geometric structure and shows considerable lumpiness in chemical distributions. The smooth central zone is evidence in favor of delayed-detonation models. The lumpiness in the outside, however, is not easily explained by any existing models of SNIa. I will also discuss CMAGIC studies of nearby SNe which results in significantly improved SN distance estimates. The analysis does not confirm the existence of a local Hubble bubble at redshift below about 7,400 km/sec.

Mar. 19, Monday 12:10 pm (TAC seminar)
Andrew Zentner,
544 Campbell Hall
"The Shape of the Dark Matter Halo of the Milky Way and Beyond"
I will focus on the shapes of the dark matter halos of galaxies. A preponderance of evidence indicates that the visible, baryonic, components of galaxies reside within the potential wells established by extended halos of dark matter. Dark matter halos are generally believed to be ellipsoidal bodies. Many techniques have been proposed to measure the shapes of the ellipsoids in which the Milky Way and other galaxies are embedded using luminous matter as a tracer of the potential. One application of this approach is to compare the inferred shapes of halos with the predictions for a statistically large sample of dark matter halos formed during numerical simulations of cosmological structure formation. As I will review, the reasoning is that the detailed shapes of halos reveal something about the nature of the dark matter as well as the amount of recent merger activity in the Universe. The result is largely a murky situation. Most theoretical approaches have ignored baryonic physics in predicting halo shapes. I will discuss the general expectations for the modifications of halo shapes when baryonic physics, thus the physics of galaxy formation, is included. I will then review recent arguments posed about the nearby satellite galaxies of the Milky Way as tracers of the large-scale Milky Way potential. Finally, I will discuss a novel method for determining the shape and orientation of the Milky Way halo to unprecedented accuracy in the coming decade using a method that is, in principle, cleaner than most other probes of halo shapes, but relies on its own set of independent assumptions.

Mar. 20, Tuesday 1:10 pm
Juerg Diemand, UCSC
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Formation and evolution of CDM halos and their substructure"
(rescheduled from the fall.) Massive supercomputer simulations now allow to follow the formation and evolution of CDM halos and their subhalo population in detail. We have recently completed the "Via Lactea" run: It resolves a Milky Way scale halo with over 200 million particles, over ten times more than the previous largest run. It resolves over 10'000 subhalos, some inside the solar circle, many sub-subhalos and the mass in substructure has still not converged, i.e. it is growing with better numerical resolution. This wealth of small scale structure has implications for direct and indirect dark matter detection, stellar streams, disk heating, gravitational lensing and the Local Group dwarf galaxy population (the "missing satellites problem").

Mar. 20, Tuesday 4:40 pm (RAL seminar)
Colin Lonsdale, MIT
501 Campbell Hall
"The Science and Technology of the MWA"
Mar. 23 Friday 12:00 pm
Mark Wise, Caltech
LBL 50-5026 (INPA Common Room)
"Imprints of a Primordial Preferred Direction on the Microwave Background"

Mar. 27 Tuesday 1:10 pm (spring break, perhaps no talk)
544 Campbell Hall (also videoconferenced to LBL 50A-5131)

February 2007:

Feb. 1, Thursday 4:10 pm (Astronomy Colloquium)
Nick Scoville , Caltech
1 Le Conte Hall
"Large Structures and Galaxy Evolution in the Cosmic Evolution Survey"
Feb. 5 Monday 12:10 pm (TAC seminar)
Hiranya Peiris, University of Chicago
544 Campbell Hall
"Understanding Cosmic Acceleration: Connecting Theory and Observation"
Cosmic acceleration at early and late times are two of the biggest mysteries confronting cosmologists today. The initial conditions of the Big-Bang are thought to have been set during ``inflation'', an era of almost exponential expansion in the primordial universe. Inflation also provides a mechanism to generate the primordial fluctuations, anisotropies imprinted into the cosmic microwave background (CMB) radiation which result in the rich structure of matter today. Current cosmological data are, for the first time, precise enough to allow detailed observational tests of inflationary models. I will describe efforts to understand the microphysics of inflation, focusing in particular on CMB data.

Intriguingly, several independent data sets show that the cosmological expansion may be once again accelerating. These observations lead to the conclusion that the universe is dominated by a negative-pressure component, ``dark energy'', which makes up roughly three-quarters of the cosmological energy density. Theoretical models for the dark energy include Einstein's cosmological constant,a dynamical component, etc. I will show how toolsfor extracting information about inflationary models can be used to constrain the physics of dark energy.

Feb. 6 Tuesday 1:10 pm
Vuk Mandic, Caltech
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Searching for Stochastic Gravitational-wave Background with LIGO: Results and Implications"
The Laser Interferometer Gravitational-wave Observatory (LIGO) has built three multi-km scale interferometers, designed to search for gravitational waves (GW). One of the targets for these searches is the stochastic GW background, whose existence is expected both due to cosmological and due to astrophysical sources. We discuss the status of LIGO, the most recent results of the search for stochastic GW radiation with LIGO interferometers, and the implications of these results for some of the theoretical models of stochastic GW background.
Feb. 8, Thursday 4:10 pm (Astronomy Colloquium)
Amy Barger , Wisconsin
1 Le Conte Hall
"The Cosmic History of AGN"
Chandra and XMM detect X-rays emitted during accretion onto supermassive black holes, even when they are highly obscured. I will present extensive multiwavelength observations of both deep and wide-area Chandra surveys that have changed our thinking on when and how supermassive black holes formed.
Feb. 9, Friday 12:00 pm, INPA Journal club
Vincent Desjacques,Hebrew University
LBNL 50-5026 (INPA conference room)
"The probability distribution of the flux in the Lya forest"
I will present a measurement of the probability distribution function (PDF) of the Lya transmitted flux at redshift 2 < z < 4 from a sample of SDSS quasars. The PDF is obtained by fitting a powerlaw continuum on a spectrum-by-spectrum basis. The SDSS data are compared to a theoretical PDF drawn from mock lognormal spectra, whose statistical properties have been constrained to match the observed Lya flux PDF and power spectrum of Keck spectra. The lognormal model fits the Keck data very well at all redshifts. However, it produces a poor fit to the SDSS data, unless large continuum correction are applied. A decrease of 15 per cent in the mean quasar continuum with a rms variance at the 20 per cent level greatly improves the fit. This strongly suggests that there is a break in the spectral slope of high-redshift quasars around the Lya emission line.

Feb. 12, Monday 12:10 pm (TAC seminar)
Rocky Kolb,
544 Campbell Hall
"Perhaps there is no dark energy and the universe is not accelerating in the usual sense"

Feb. 13 Tuesday 1:10 pm
Kendrick Smith, University of Chicago
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"CMB polarization: past, present, and future"
Obtaining precision measurements of CMB polarization power spectra will be an important frontier for cosmology in the upcoming decade, with many experiments in an operational or funded state. In this talk, we first present a status update from analyzing the most recent season of observations from the CAPMAP experiment. We then describe the upcoming QUIET experiment, scheduled to begin taking data in late 2007. Finally, we present recently-proposed improvements to the usual (pseudo-$C_l$) framework for rapidly estimating polarization power spectra from data. These improvements help automate power spectrum estimation, and can also significantly improve B-mode uncertainties at low noise levels anticipated for next-generation experiments.

Feb. 14, Wednesday 12:10 pm (Wed theory lunch)
Christy Pierce, UCSC
501 Campbell Hall
"AGN Host Galaxy Morphologies"
Current models of AGN feedback make specific predictions about observable properties of AGN involved in galaxy interactions. I present recent results of a study of the morphologies of active galactic nucleus (AGN) host galaxies. The AGN studied have been chosen using four distinct methods and are taken from two well-studied regions - the Hubble Deep Field North and the Extended Groth Strip. We find that AGN are more likely to be hosted by galaxies with disturbed morphologies and less likely to be hosted by Sc/d/Irr galaxies than galaxies not hosting AGN. Our results are consistent with the general prediction that AGN are more closely associated with morphologically interacting galaxies than a sample of non-AGN, however, specific predictions about obscuration levels (as suggested by X-ray detections and infrared colors) are not consistent with our observations. In addition, I present results of a test of the validity of our morphology measurements of AGN hosts (the optical point source often associated with an AGN may affect the morphology measurement). These results are quantified by way of an estimation of how our first results should change.
Feb. 15, Thursday 4:10 pm (Astronomy Colloquium)
Fred Lo , NRAO
1 Le Conte Hall
"Mega-masers, Hubble Constant and Dark Energy"
Powerful water maser emission (water mega-masers) can be found in accretion disks in the nuclei of some galaxies. Besides providing a measure of the mass at the nucleus, such mega-masers can be used to determine the distance to the host galaxy, based on a simple dynamical model. Such mega-masers are useful for determining the Hubble Constant, independent of the traditional approach based on Cepheid variables. We will explain the importance of determining the Hubble Constant to high accuracy for constraining the equation of state of Dark Energy and describe the Mega-maser Cosmology Project that has the goal of determining the Hubble Constant to better than 3%. Time permitting, we will also present the scientific capabilities of the current and future NRAO facilities for addressing key astrophysical problems.
Feb. 16, Friday 12:00 pm, INPA Journal club
Rychard Bouwens,UCSC
LBNL 50-5026 (INPA conference room)
"Galaxy Buildup During the First 1.5 Billion Years of Cosmic History"
Just four years ago, only a few high redshift galaxies were known within the first billion years. However, since then, sufficient HST ACS and NICMOS data have been taken that we can construct very large samples of galaxies at early times and study the evolution of the rest-frame UV LF all the way out to redshifts of 8 -- just 700 million years after the Big Band. The larger, more statistically significant samples come from the deep, wide-area ACS data (including more than 4800, 1500, and 600 galaxies at redshifts of 4, 5, and 6, respectively), allowing us to come to firm conclusions about how the luminosity function of galaxies evolves at very early times. Our own analyses demonstrate that the faint-end slopes of these luminosity functions are remarkably uniform and steep (alpha = -1.7), indicating little evolution from z~6 => z~4. On the other hand, the characteristic luminosity L* of galaxies brightens considerably over this period, demonstrating that the galaxy population actually builds up quite dramatically at early times -- exactly as we might have expected from popular hierarchical models of galaxy formation. Pushing back even further in cosmic history to 400-700 million years after the Big Bang, we also have detected galaxies at z~7-8 in deep NICMOS observations and set limits at z~10 directly. Spitzer observations of our z~7-8 sample have been used to estimate masses and ages, suggesting substantial formation as early as z~9-10. Our high-redshift findings strongly suggest that the evolution we see at z~4-6 continues into the reionization epoch.

Feb. 20 Tuesday 11:15 am
Avi Loeb, Harvard-Smithsonian, CfA
6th floor lounge, Campbell Hall
"Informal and brief (20 min) discussion on 21 cm line and cosmology"

Feb. 20 Tuesday 1:10 pm
Charlie Conroy, Princeton
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"The co-evolution of galaxies and dark matter halos"
The current cosmological paradigm (and its associated parameters) provides us with a well-defined dark matter skeleton on top of which the formation and evolution of galaxies must take place. I will focus on recent attempts to relate galaxies to dark matter halos from z=0 to z=5 and what such relations might tell us about the build-up of massive galaxies, the intracluster light, and the survival and destruction rate of satellite galaxies and luminous red galaxies (LRGs).

Feb. 21, Wednesday 12:00 pm, INPA Journal club
Daniel Grin, Caltech
LBNL 50A-5132 (director's conference room)
"A Telescope Search for Decaying Relic Axions"
I will summarize the techniques and results of a recent telescope search for optical emission decaying relic axions using the VIMOS IFU at the VLT. Relevant theory will be reviewed and new limits on the axion's coupling to two photons will be discussed. If time permits, I will review cosmological limits to axion masses, and briefly how they may be evaded in extended reheating scenarios.

Feb. 21, Wednesday 12:10 pm, special TAC seminar
Avi Loeb, Harvard-Smithsonian CfA
544 Campbell Hall
"Key Questions on Black Holes in Galaxies"
Recent data indicates that almost all galaxies possess a supermassive black hole at their center. When gas accretes onto such black holes it heats-up and shines, resulting in the appearance of a bright quasar. The earliest quasars are found to exist only a billion years after the big bang. I will describe recent observations of both the nearest and the most distant supermassive black holes in the universe. The formation and evolution of the black hole population can be described in the context of popular models for galaxy formation. I will describe the key questions that drive current research on supermassive black holes and present theoretical work on the radiative and hydrodynamic effects that quasars have on their cosmic habitat. Within the coming decade it would be possible to test general relativity by monitoring and possibly even imaging the polarized emission from hot spots around the black hole in the center of our Galaxy, SgrA*.

Feb. 23, Friday 12:00 pm, INPA Journal club
Matthew Francis, University of Sydney
LBNL 50-5026 (INPA conference room)
"Cosmological Structure: The Effects of Dark Energy"
One of the ways in which the hypothesised dark energy causing the acceleration of the expansion of the universe imprints its presence is through the growth of large scale structure. The properties of dark energy can be parametrised through its equation of state w(z), and different models for the equation of state will trace a different growth history observable though the matter power spectrum. As the accuracy of cosmological observations improve, so must the accuracy of simulations used to model the effects of dark energy. In this talk I will give a brief review of structure formation and N-body simulations as well as present recent work on the effects of a two parameter dynamic dark energy model on the matter power spectrum.

Feb. 26 Monday 2:30 pm
Katie Freese, U. Michigan
402 Old LeConte (particle theory seminar)
"Naturalness in Inflation"
Feb. 27 Tuesday 1:10 pm
Andrew Liddle, Sussex and Hawaii
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Model selection and Dark Energy"
Many of the key questions in cosmology concern deciding which set of parameters are needed to fit data, without caring too much about actual parameter values. In statistical terminology, they are model selection questions. I review the model selection methodology, particularly its Bayesian versions, and show how it can be applied to a range of astrophysical problems, both in analysis of existing data and in forecasting the abilities of upcoming experiments.

January 2007:

Jan. 4 Thursday 2:30 pm
R. Ali Vanderveld, Cornell
LBL 50A-5132
"Corrections to the Measured Expansion History due to Local Cosmological Inhomogeneity"
I will discuss some of the ways that local cosmological inhomogeneity has been found to affect our interpretation of the measurements of the redshifts and luminosity distances of Type Ia supernovae. This discussion will then focus on the systematic corrections that one would find even for very large sample sizes as a result of the "fitting problem", wherein the fitting of data to what we would see in a homogeneous universe introduces errors due to the nonlinearity of general relativity. I will also address the recent claim that this effect could be large enough to explain the seemingly anomalous supernova data without the need to introduce dark energy or modified gravity.

Jan. 16 Tuesday 1:10 pm
Anja von der Linden, Garching
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"How special are Brightest Cluster Galaxies?"
We investigate how the systematic properties of Brightest Group and Cluster Galaxies (BCGs) depend on stellar mass and on their privileged location near the cluster center. We have used the Sloan Digital Sky Survey to construct a sample of 625 BCGs together with control samples of non-BCGs matched in stellar mass, redshift, and color, in order to disentangle these influences. At all stellar masses, BCGs are more likely to host a radio-loud AGN. BCGs contain a larger fraction of dark matter than non-BCGs, and their dynamical mass-to-light ratio varies less as a function of galaxy luminosity, implying that early-type BCGs follow a different fundamental plane than ordinary elliptical galaxies. Also, BCGs follow a steeper Faber-Jackson relation than non-BCGs, as suggested by models in which BCGs assemble via dissipationless mergers along preferentially radial orbits. We find tentative evidence that this steepening is stronger in more massive clusters.

Jan. 16 Tuesday 4:00 pm (RPM)
Ira Wasserman, Cornell
LBL 50A-5132
"Dynamics of the R-Mode Instability of Accreting Neutron Stars"
Rotating neutron stars have modes that are driven unstable by gravitational radiation reaction, principally the ``R-mode'', a Rossby wave with L=m=2, hence large gravitational radiation reaction. It has been suggested that the R-mode instability is what sets the largest angular frequency of rotation of accreting neutron stars. This maximum frequency depends on the neutron star composition via viscous dissipation and neutrino cooling, and so is a probe of the high density nuclear physics of neutron stars. The nonlinear development of the instability plays a very important role in determining how this process works, and also illustrates how instabilities can saturate at low amplitudes as a consequence of nearly resonant excitation of other modes. The saturation amplitude limits the prospects for detecting gravitational radiation from R-mode unstable neutron stars.

Jan. 17 Wednesday 1:30 pm
Jakob Jonsson, Stockholm
LBL 50B-4205
"Estimating the magnification of weakly lensed supernovae"
Light from distant sources is affected by the matter distribution along the line-of-sight. The gravitational fields of intervening galaxy haloes give rise to deflection of light rays, which can result in amplification or de-amplification of the flux from distant sources. Gravitational lensing will thus add extra scatter to standard candles. If possible to accurately predict the (de-)amplification of standard candles, the observed brightness scatter at very high redshifts might be reduced. Simulations suggest that is is possible to reduce the dispersion of lensed standard candles by estimating the mass of foreground galaxies for which we have good spectroscopic and/or photometric information. The method of "weighting" galaxies along the line-of-sight to estimate the magnification factor has been applied to Type Ia supernovae in the GOODS fields. The brightness of these supernovae seem to correlate with the calculated lensing magnification, as expected. Gravitational lensing would also affect gravitational wave standard sirens (the analogy of standard candles). Correcting standard sirens for gravitational lensing could improve the cosmological constraints attainable by LISA.

Jan. 19 Friday 10:30am-3:30 pm
Dark Energy From Fundamentals
Workshop at LBL

Jan. 22 Monday 12:10 pm (TAC seminar)
Avishai Dekel, Racah Inst. of Physics and UCSC
544 Campbell Hall
"Maximum Starbursts without Mergers"

Jan. 22 Monday 4:30 pm (Physics Colloquium)
Steve Furlanetto, Yale
1 LeConte Hall
"Cosmology at Low Radio Frequencies: The 21 cm Transition" (note PDF is 50 Mb)
Some of the greatest mysteries remaining in cosmology concern the growth of structure during the cosmic dark ages between the last scattering of the cosmic microwave background and the galaxy-dominated era we live in. Soon a new set of low-frequency radio telescopes will begin probing this era by studying the redshifted hyperfine transition of neutral hydrogen in the intergalactic medium. I will describe what we hope to learn about the dark ages, the first galaxies, and cosmic reionization from these observations, as well as the unique challenges posed by the measurements.

Jan. 23 Tuesday 1:10 pm
Marc Seigar, UCI
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Constraining Dark Matter Halo Profiles and Galaxy Formation Models Using Spiral Arm Morphology"
In this presentation, I will investigate the use of spiral arm pitch angles as a probe of disk galaxy mass profiles. I will present confirmation of a previous result that spiral arm pitch angles (P) are well-correlated with the rate of shear (S) in disk galaxy rotation curves, by using a much larger sample (51 galaxies) than used previously (17 galaxies). This correlation is used to argue that imaging data alone can provide a powerful probe of galactic mass distributions out to large lookback times. In contrast to previous work, I will show that observed spiral arm pitch angles are independent of the wavelength at which they are measured (from 0.4 to 2.2 microns) and use this to strengthen the known correlation between spiral arm pitch angle and rotation curve shear, using B-band images. We then use some example galaxies to demonstrate how an inferred shear rate (S) coupled with a bulge-disk decomposition model and a Tully-Fisher derived velocity normalization can be used to place powerful constraints on a galaxy's baryon fraction and dark matter halo profile. These techniques have also been applied to the Andromeda Galaxy as a test case.
Jan. 23 Tuesday 4:00 pm
Mark Brodwin, JPL
LBNL 50A-5132
"A Large Population of High Redshift Galaxy Clusters"
Using a probabilistic photometric redshift-based approach combining Spitzer mid-IR and NOAO optical data, we have discovered nearly 300 new galaxy clusters and groups in the NDWFS Bootes field, nearly 100 of which are at 1<2. To date we have spectroscopically confirmed 8 of these high redshift clusters, spanning 1.06 < z < 1.41. In this regime clusters have the mean colors predicted by a passive evolution model with a high (z>3) formation redshift. Deep follow-up IRAC and ACS data, currently being obtained for 18 of the z>1 clusters, allows detailed studies of the mass assembly history in massive galaxies at this key epoch.

Jan. 25, Thursday 4:10 pm (Astronomy Colloquium)
Bob Kirschner , Harvard
1 Le Conte Hall
"Fundamentals of Supernova Cosmology"
Supernova observations form the foundation of evidence for an accelerating universe. Diligent work on supernova spectroscopy and supernova photometry in the nearby Universe allows for tests of some of the assumptions that make supernovae so powerful at high redshift. They also provide unique probes of the local dark matter distribution through measurement of local flows. The current state of the CfA program at low-z, the ESSENCE program at intermediate redshift, and the Higher-Z program with the HST will be discussed, and the best inferences for the properties of dark energy presented. A flat universe with a cosmological constant for the dark energy is consistent with all the current constraints.

Jan. 30 Tuesday 1:10 pm
Miguel Morales, MIT
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Observing the Epoch of Reionization"
Highly redshifted 21 cm emission from the Epoch of Reionization (EOR) is a unique cosmological probe, and upcoming EOR radio observations could revolutionize our understanding of structure formation and the emergence of the first luminous objects. However, 21 cm EOR observations are complicated by strong foreground contamination and stringent instrumental requirements. In this talk, I will review the observational signatures of the Epoch of Reionization and how the faint 21 cm emission can be extracted from the foreground signals, and describe the Mileura Widefield Array - Low Frequency Demonstrator (MWA-LFD) my colleagues and I are constructing in Western Australia.

December 2006:

Dec. 1, Friday 12:00 pm, INPA Journal club
Kristen Shapiro, UCB
LBNL 50-5026 (INPA conference room)
"Testing Mass Assembly in the Early Universe"
I will present recent results from the SINS study of spatially resolved galaxy kinematics at z~2. This observing program is made possible by the new class of integral-field spectrographs that operate in the infrared with high spatial and spectral resolution. I will discuss how these instruments, coupled with recently-available adaptive optics systems on 10-m class telescopes, enable us to probe in detail galaxy formation in the early Universe. Such studies reveal a surprising Universe, in which massive disks are already in place, after an apparent very rapid assembly. I will focus primarily on our observations of BzK-15504, which represent the highest spatial resolution study of a z~2 galaxy to date and which give us insight into mass assembly, star formation trigger mechanisms, and bulge formation in the early Universe.

Dec. 4, Monday 12:10 pm (TAC seminar)
Mariska Kriek, Leiden
544 Campbell Hall
"Clues on Massive Galaxy Formation at z~2.5 from NIR spectroscopy"
The past few years have seen a tremendous increase in our knowledge of the galaxy population at z < 3. Recently it was found that red galaxies make up more than 2/3 of the most massive galaxies in this redshift range. As most of these galaxies are beyond the limits of optical spectroscopy they are underrepresented in available spectroscopic samples of high redshift galaxies. To obtain a full spectroscopic census of the Universe at z~2.5 we have performed a near-infrared spectroscopic survey of an unbiased, K-selected sample with GNIRS on Gemini-South. I will present the results of this program and follow-up SINFONI integral field spectroscopy, Spitzer and NICMOS imaging and discuss the implications for the formation of massive galaxies.

Dec. 5 Tuesday 1:10 pm
Mark Brodwin, JPL
544 Campbell Hall (also videoconferenced to LBL 50B-5131)
please note videoconferencing room change!

"A Large Population of High Redshift Galaxy Clusters" (warning: pdf is 50Mb)
Using a probabilistic photometric redshift-based approach combining Spitzer mid-IR and NOAO optical data, we have discovered nearly 300 new galaxy clusters and groups in the NDWFS Bootes field, nearly 100 of which are at 13) formation redshift. Deep follow-up IRAC and ACS data, currently being obtained for 18 of the z>1 clusters, allows detailed studies of the mass assembly history in massive galaxies at this key epoch.

Dec. 12 Tuesday 4:00 pm
Adam Bolton, Harvard Smithsonian CfA
LBL 50A-5132
"Strong Lensing and Fundamental Physics"
The scientific applications of strong gravitational lensing can be divided into two categories, which we may call "fundamental" and "astrophysical". Fundamental applications include tests of general relativity, geometric and scale-factor cosmology, and existential questions about dark matter; astrophysical applications encompass all lensing-enabled studies of the nature and evolution of the lensing and lensed objects. Fundamental and astrophysical lensing applications often present themselves in degenerate pairs: one can only derive the fundamental result if one assumes the astrophysical result, or vice versa. In this talk, I will describe a number of fundamental applications of strong lensing on the scale of individual galaxies, for which I will import astrophysical results only as necessary. I will focus in particular on new fundamental studies and results enabled by recent advances in observational astronomy, such as the large sample of strong galaxy-galaxy lenses that we have identified with the Sloan Lens ACS Survey.

Dec. 14 Thursday 4:00 pm
Marusa Bradac, KIPAC
LBL 50A-5132
"Dark matter and the highest redshift galaxies: measuring the invisible with gravitational lensing"
One of the most important outstanding quests in cosmology is the understanding of the formation and evolution of galaxies and galaxy clusters. In particular, we seek to answer what the dark matter is, what are its properties, and how it shapes galaxies and galaxy clusters through cosmic time. Whereas the currently accepted paradigm for dark matter works well, discrepancies between model predictions and observations (such as the abundance of substructure in halos, and dark matter profile shapes) still remain. In this talk I will address these issues with gravitational lensing. In particular, I will show how I study the properties and the presence of (dark matter) substructure in galaxies, and how I use galaxy clusters as laboratories for dark matter. Further, using clusters as gravitational telescopes I will show some preliminary results of the search for highest redshift objects. The role of high resolution observations (HST now and SNAP in the future) is the key part of these projects and will shed the light on dark matter and high redshift galaxies, currently still part of the ``invisible'' Universe.
Dec. 15, Friday 12:00 pm, INPA Journal club
Kyle Dawson,LBNL
LBNL 50-5026 (INPA conference room)
"Decelerating and Dustfree: Targeting SNe Ia in High Redshift Galaxy Clusters"
The SCP is pursuing a novel approach to obtaining Type Ia supernovae (SNe Ia) at very high redshifts (z>~1). In a 219 orbit cycle 14 program (HST-GO 10496), we are using the Advanced Camera for Surveys (ACS) and NICMOS on the Hubble Space Telescope (HST) to repeatedly observe massive galaxy clusters at z>~1 to find and follow SNe. Clusters of galaxies are known to be dominated by nearly dust-free early type galaxies. SNe discovered in these galaxies are expected to have negligible dust extinction, the largest source of both statistical and systematic uncertainty in SNe derived distances. In addition, galaxy clusters contain a population of early type galaxies at a density approximately five times that in the high redshift field, leading to a much higher rate of detection of SNe Ia in this well-understood host environment. With 20 scheduled half-nights on the Subaru telecope as well as multiple nights on the Keck and VLT telescopes, we are obtaining spectroscopic confirmation and redshift of newly discovered SNe and their hosts. This data will significantly improve supernova constraints of dark energy both in terms of statistical uncertainty, and perhaps more importantly, of systematic uncertainty. This sample of more than 20 galaxy clusters is also being studied for weak lensing, galaxy morphology, and color-magnitude relationship, as part of an entire program of cluster studies.
In this talk I will describe the survey which concluded just last week. I will present some preliminary results and describe the various projects that our group is planning with this data set.

Dec. 18 Monday 4:00 pm
Alexie Leauthaud, Marseille
LBL 50B-4205
"The Link Between Galaxies and their Dark Matter Haloes"
To what extent does the surrounding dark matter environment shape the observational properties of luminous galaxies? In an attempt to shed further light on this question, I will present early results from a lensing analysis undertaken in the COSMOS field (Scoville et al. 2006). Weak gravitational lensing techniques have the unique ability to probe the full dark matter distribution and to reveal how galaxies are related to their dark matter haloes. Using the galaxy-galaxy lensing technique, I have mapped dark matter around an ensemble of galaxies and groups of galaxies within the COSMOS field. Using the exqusite ACS imaging to classify galaxies according to their morphology, I will show that the dark matter environment does indeed play a role in shaping the galaxies that we observe. Measuring this connection is not only a powerful test of the CDM paradigm, but also provides an essential ingredient towards understanding the physics of galaxy formation.

November 2006:
Nov. 6, Monday 12:10 pm (TAC seminar)
Jonathan Pritchard, Caltech
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Radiation backgrounds from the first sources and the redshifted 21 cm signal"
Observations of the redshifted 21 cm line offer a promising probe of early radiation backgrounds. Anisotropies in the 21 cm signal arise from fluctuations in the IGM temperature, density, and neutral fraction and through the Lyman alpha flux. These fluctuations contain a wealth of information on the background radiation field at UV and X-ray frequencies. Before reionization, spatial variation in the Lyman alpha flux from the first sources imprints information about the source distribution on the 21 cm signal. Later, as the IGM is heated by X-rays, inhomogeneous heating leads to gas temperature fluctuations whose detection could constrain the luminosity and spectrum of the first X-ray sources. In this talk, I will discuss theoretical models for both of these mechanisms and outline the possiblities for detection with future experiments.

Nov. 7, Tuesday 1:10 pm
Gabriella De Lucia, Garching
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"The colour-magnitude relation in galaxy clusters from z=0.8 to z=0"
I will present recent results from the ESO Distant Cluster Survey on the build-up of the colour-magnitude relation since z~0.8. While red-sequence galaxies in all these clusters are well described by an old, passively evolving population, we confirm our previous finding of a significant evolution in their luminosity distribution as a function of redshift. I will discuss the results obtained in the context of modern semi-analytic models of galaxy formation and evolution.

Nov. 9, Thursday 4:10 pm (Astronomy Colloquium)
Aparna Venkatesan , USF
2 Le Conte Hall
The First Stars in the Universe: Formation, Feedback Effects and Detections
I will present the role played by the first stars in the reionization and metal enrichment of the early universe. Primordial stellar objects have unique characteristics that can be identified through their ionizing properties and the elements created by their supernovae. By combining these two signatures with current data on reionization, the microwave background, and the detection of metals in a variety of high-redshift and local environments, we can obtain relatively strong constraints on the mass function and ionizing efficiencies of the first stars. I will discuss when and how the transition from first- to second-generation star formation could occur in primordial galaxies, and the role played by the radiative transport of dust from the first supernovae in this transition. The fossil signatures of this process may have already been detected in the current nucleosynthetic data on Galactic extremely metal-poor halo stars. This data also reveals an interesting coincidence in the cosmological milestones of reionization and the end of the first-stars era. I will end with suggesting a multiwavelength observational program that could constrain the epochs and properties of primordial stellar clusters.

Nov. 10, Friday 12:00 pm, INPA Journal club
Francisco Prada,IAA-CSIC
LBNL 50-5026 (INPA conference room)
Halo properties of isolated galaxies
In this talk I will discuss the progress we have made on the knowledge of the properties of dark matter halos of isolated galaxies. Using the SDSS, we probe the halo mass distribution at large radii, by studying the motions of satellites around isolated galaxies. We find direct observational evidence of the dark matter density decline in the peripheral parts of galaxies as predicted by the LCDM paradigm; we also note that this result contradicts alternative theories of gravity such as MOND. We measure the virial mass-to-light and virial-to-stellar mass ratios of L* galaxies and study the evolution in their halo masses between z=1 and z=0 by combining data from the DEEP2 galaxy redshift survey and the SDSS. Other properties of satellites will be discussed. Finally, I will comment on the study we have performed on the outer structure of galactic dark matter halos and their mass growth in high-resolution cosmological simulations.
Nov. 10, Friday 2:00 pm, half hour informal talk
Francisco Prada,IAA-CSIC
LBNL 50-5026 (INPA conference room)
"Future plans for the Spanish 10-m telescope"

Nov. 13, Monday 12:10 pm (TAC seminar)
Glennys Farrar, NYU
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"A new force in the Dark Sector?"
The dynamics of dark matter is studied using the massive cluster of galaxies 1E0657-56. The velocity of the ``bullet" subcluster has been measured by X-ray emission from the shock front, and the masses and separation of the main and sub-clusters have been measured by gravitational lensing. The velocity with gravity alone is calculated in a variety of models of the initial conditions, mass distribution and accretion history; it is much higher than expected, by at least 2.4 sigma. The probability of so large a subcluster velocity in cosmological simulations is, following Hayashi and White, < 10^{-7}. A long range force with strength ~ 0.4 - 0.8 times that of gravity would provide the needed additional acceleration.

Nov. 14, Tuesday 1:10 pm
Jaiyul Yoo, Ohio State
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Constraining the Dark Side of the Universe"
I focus on characterizing the clustering of dark matter and understanding the nature of dark energy. Based on the halo occupation distribution (HOD) framework, I 1) develop an analytic model for combining galaxy-galaxy lensing and galaxy clustering on small scales to constrain the matter density parameter and the matter fluctuation amplitude, 2) construct scale-dependent bias shapes using constraints from galaxy clustering to improve estimates of the linear matter power spectrum, and 3) develop an analytic model to predict the dependence of cluster-galaxy lensing signals on cosmological parameters. I apply the analytic models to the SDSS measurements to probe the dark side of the Universe. Finally, I discuss the prospect of these methods and applications to future wide-field imaging surveys.

Nov. 15, Wednesday 12:10 pm (Wed. Theory Lunch)
Yuexing Li, Harvard-Smithsonian CfA
544 Campbell Hall
"The formation and evolution of galaxies and quasars at z~6"
The discoveries of luminous quasars at z~6 challenge theoretical models to explain the early formation of supermassive black holes and massive galaxies when the Universe was less than 1 billion years old. I'll present the first multi-scale simulations that, together with a self-regulated model for the SMBH growth, produce a luminous quasar at z ~ 6.5 in the LCDM cosmology, which resembles the most distant quasar observed, SDSS J1148+5251. The IR calculations show that this quasar at z~6.5 has a SED that is similar to that of J1148, and that the system evolves from cold ULIRG to warm ULIRG as it transforms from starburst to quasar. Furthermore, the ionization from stars is found to be significant. Large HII regions of up to 10 Mpc by stars were already in place before the peak quasar activity, suggesting that stars may play a more important role in reionization than quasars.

Nov. 15, Wednesday 4:00 pm (Interdisciplinary Instrumentationn Colloquium)
Helmuth Spieler, LBNL
LBNL, Building 50 Auditorium
"Large-Scale Bolometer Arrays for Next-Generation CMB Experiments"
Large bolometer arrays are required to provide the sensitivity for next-generation CMB experiments. This talk describes developments by the UCB-LBNL group for CMB anisotropy and polarization measurements. Superconducting transition-edge sensors operating at about 0.3K in combination with SQUID amplifiers provide the required sensitivity. Monolithic fabrication techniques integrate polarization-sensitive antennas, bandpass filters, and bolometers to measure both polarizations in each pixel. The readout utilizes a novel frequency-domain multiplexing technique. Complete systems for both APEX-SZ on the Atacama plateau in Chile and the South Pole Telescope will be fielded this winter. The technology has also been applied to precision x-ray and gamma-ray detection.
Nov. 20, Monday 4:30 pm
George Smoot, UCB
1 Le Conte Hall "COBE, CMB & Cosmology"
COBE was a watershed set of observations that launched the era we refer to as precision cosmology. Prior to COBE were a series of theoretical ideas and observations that helped shape the landscape and prepare the way for COBE and the avalanche of CMB instruments' observations and other cosmological observations. It is interesting to review the 40 years of CMB observations and those predicted for the next few years to see the rapid development of cosmology in recent years and what the future is likely to hold.
Nov. 21, Tuesday 1:10 pm
Sara Ellison, U Victoria
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Metals, Dust and Diffuse Interstellar Bands in High Redshift Galaxies"
Although astronomers can now routinely find galaxies out to redshifts of 3 and beyond, searches which rely on detecting starlight are necessarily biased towards the brightest galaxies. Studying galaxies via the absorption signatures which they imprint upon background quasars provides us with a powerful, alternative tool to observe ALL galaxies, independent of their luminosity. I will summarise the use of this technique and some of the insights that quasar absorption line spectroscopy has given us into the census of gas, metals and dust at high redshift. Although two decades of observations have now led us to the conclusion that the majority of the gas reservoirs at high redshift are poor in metals, I will discuss a project designed to find rare, highly enriched galaxies which is yielding many surprising results at a lookback time of 10 gigayears.

Nov. 22, Wednesday 12:10 pm (Wed. Theory Lunch)
Marilena LoVerde, Columbia
501 Campbell Hall Please note room correction!
"Cosmic Magnification and the ISW Effect- New Rules for High-Redshift Observations"
The ISW effect is a secondary anisotropy in the CMB that has proven to be an interesting probe of dark energy. This effect is isolated from primary anisotropies by cross-correlating the CMB temperature anisotropies with matter anisotropies inferred from galaxy counts. However, at high redshifts, number counts are modified by magnification bias. I will discuss how magnification can greatly alter the scale dependence and magnitude of cross-correlation measurements and if ignored would lead to erroneous conclusions about dark energy.

Nov. 27, Monday 3:10 pm (TAC seminar),rescheduled due to flight delay.
Ivo Labbe, Carnegie
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"The formation histories and structures of massive galaxies at z > 2"
One of the premier unsolved questions in cosmology is how massive galaxies assembled their stars and central black holes. Multiwavelength observations are now enabling us to address these questions directly by studying massive galaxies during their main formation epoch z = 1.5 - 3. Deep infrared imaging from Spitzer is playing a fundamental role in these studies. I will discuss the constraints placed by IRAC, MIPS, and X-ray observations on the stellar populations and AGN activity in this crucial redshift range. A particular striking result is the photometric identification of massive old galaxies at z>2 with very low specific star formation rates, which appear to make up 30-40% of z~2.5 galaxies at the high mass end. Our follow-up studies with NICMOS show that these old massive galaxies have remarkable structural properties, presenting us with new puzzles about their structural evolution to low redshift. Pushing to even higher redshifts, the unprecedented sensitivity of Spitzer/IRAC has allowed us to probe the stellar-masses and ages of galaxies at z > 7 in the Ultra Deep Field, providing a glimpse of the earliest phases of galaxy formation. I will place these results in the context of formation scenarios for massive galaxies, and look ahead to the future with the expected launch of the far-IR Herschel Telescope, and the installation of WFC3 on Hubble in the next 18 months.

Nov. 28, Tuesday 1:10 pm
Douglas Rudd, University of Chicago
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"The Influence of Baryons and Dissipation on the Matter Power Spectrum"
The evolution of the matter power spectrum has been well studied using collision-less dark matter simulations. Future weak-lensing experiments will measure the power spectrum at moderate (k ~ 1 h/Mpc) scales with percent level accuracy, a regime where the influence of dissipational baryons become important. I will discuss current cosmological simulations which include baryonic physical processes, and demonstrate that these processes have important effects on the structure of dark matter halos and a measurable effect on the matter power spectrum. In addition, I will discuss modifying the halo model framework to include baryons and study their effect on the power spectrum.

Nov. 29, Wednesday 12:10 pm (Wed. Theory Lunch)
Kai Noeske, UCSC
501 Campbell Hall
"Star formation in field galaxies since z~1: A new picture from AEGIS"
I present a comprehensive view of star formation since z~1 in massive field galaxies. For ~3000 galaxies in the All Wavelength Extended Groth Strip Survey" (AEGIS), we combine UV-to-IR star formation rate tracers, stellar masses, quantitative HST morphologies and rest-frame photometry. Galaxies segregate into a fiducial star-forming population, and red and dead galaxies or LINER candidates. The majority of star-forming galaxies form a distinct "Main Sequence", with a narrow range of star formation rates at a given mass and redshift. The range of star formation (1) limits the amplitude of episodic star formation; (2) constrains the effect of major mergers; (3) shows that a gradual decrease of star formation in most galaxies dominated since z~1, not a decrease of strong starbursts; (4) shows Luminous Infrared galaxies at z~1 to be mostly normal star-forming galaxies, not strong bursts. This gradual decrease of star formation can be reproduced by a model of gas exhaustion with timescales increasing to less massive galaxies, quantifying mass dependencies of star formation histories. The data and models also indicate a new picture of "staged galaxy formation", where the onset of major star formation shifts to lower redshifts for less massive galaxies.

October 2006:

Oct. 3, Tuesday 1:10 pm
Michael Niemack, Princeton
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"The Atacama Cosmology Telescope (ACT)"
ACT will measure the temperature fluctuations of the CMB on arcminute to degree scales. Measuring these angular scales will allow us to probe the primary CMB anisotropies as well as explore secondary mechanisms such as the Sunyaev-Zeldovich effects, the Ostriker-Vishniac effect, and gravitational lensing of the CMB. These measurements, combined with optical and X-ray follow up observations, will allow us to constrain the equation of state and the neutrino mass, and to study the growth of structure and ionization history of the universe. ACT observations are scheduled to begin in 2007 with the installation of the Millimeter Bolometer Array Camera (MBAC). MBAC will consist of three kilopixel arrays of TES bolometers operated at 145, 220, and 265 GHz. We will discuss the design, testing, and status of the experiment as well as recent sky measurements made with our prototype instrument.

Oct. 10, Tuesday 4:10 p.m.,
Jim Peebles, Princeton, Hitchcock Lecture
International House Auditorium, 2299 Piedmont Avenue, Berkeley
"Exploring the Large-Scale Nature of the Universe"

Oct. 11, Wednesday 4:10 p.m.,
Jim Peebles, Princeton, Hitchcock Lecture
International House Auditorium, 2299 Piedmont Avenue, Berkeley
"Triumphs and Challenges for Modern Cosmology"

Oct. 12, Thursday 4:10 pm (Astronomy Colloquium)
Jim Peebles , Princeton
2 Le Conte Hall
"The Dark Sector of Cosmology: Successes and Challenges"
We have good evidence for the reality of dark matter and dark energy, but not many constraints on the properties of this dark sector. I will describe observations that suggest to me that the physics of the dark sector is more complicated than the simplest default model, suggest an an adjustment of the physics that seems to improve the situation, and discuss the prospects for further tests.

Oct. 13, Friday 2:00 pm, INPA Journal club
Robert Quimby, UT Austin
LBNL 50-5026 (INPA conference room)
"The Texas Supernova Search"
Supernovae (SNe) are popular tools to explore the cosmological expansion of the Universe owing to their bright peak magnitudes and reasonably high rates; however, even the relatively homogeneous Type Ia supernovae are not perfect standard candles intrinsically. Their absolute peak brightness must be established by corrections that have been largely empirical. Hundreds of SNe are now found every year, shrinking the statistical errors in the cosmological terms, but most of these distant discoveries do little to further the physical understanding of SNe, which may illuminate unknown systematics.
This talk will describe recent results from the The Texas Supernova Search, a campaign designed to discover not the most SNe nor the most distant SNe, but instead to amass a small collection of well-observed nearby SNe with detailed, multi-epoch spectral observations beginning at the earliest possible phases. For the past two years, we have pointed ROTSE-IIIb's 1.85 x 1.85 degree field of view at nearby galaxy clusters and searched thousands of galaxies, covering hundreds of square degrees on the sky, for supernovae. With ToO time on the neighboring 9.2m Hobby-Eberly Telescope, we have captured SNe spectra at some of the earliest phases ever. I will discuss the implications of these data on the physics of SNe explosions, including the propagation of the burning front and the progenitors of Type Ia supernovae.

Oct. 13, Friday 3:00 pm, SSL Colloquium
Uwe Oberlack, Rice
SSL Addition Conference Room
"Bringing light to the dark universe: the hunt for WIMP dark matter"
A wealth of astrophysical and cosmological evidence indicates that we are living in a dark universe. Almost everything we know, the matter that surrounds us and that we are made of, the matter in stars, all of which consisting of quarks and electrons, are a mere 4% of the content of the universe. We are the exotic matter in a sea of normal, dark, non-baryonic, and as yet unknown matter and some even larger fraction of "normal" but even lesser known dark energy. Zwicky gave us a head start on learning about the existence of Dark Matter some seven decades ago compared to the rather recent discovery of Dark Energy. It is the stunning coincidence of the lessons learned from astrophysics (dominance of non-baryonic "cold" DM and its distribution) and the lessons learned from particle physics, suggesting a yet to be verified symmetry of nature called supersymmetry, that identify a particularly convincing candidate for the missing Dark Matter particle. Weakly Interacting Massive Particles (WIMPs) in the form of stable neutralinos are a natural consequence of so-called supersymmetric extensions of the Standard Model of elementary particles. A significant number of collaborations with detectors of various technologies are participating in the search for the elusive DM particle. The challenges of background and low rates are considerable, requiring ever more sophisticated techniques of particle detection, discrimination, and shielding. I will review the status and outlook of some of the current techniques employed, including recent developments with the XENON Dark Matter Project.

Oct. 17, Tuesday 1:10 pm
Oliver Zahn, Harvard
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Illuminating the Universe: New Probes of Reionization and Cosmology"
Reionization is one of the most interesting eras of cosmological structure formation. I will talk about ongoing theoretical advances made to better understand the epoch. Beyond state-of-the-art radiative transfer simulations, I will emphasize the important role analytic modeling plays in guiding our physical intuition. I will then discuss some unique statistical properties of the redshifted 21 cm signal, a reionization observable with great potential. For 21 cm and beyond, a number of conceived experiments should deliver a wealth of information, including information about the cosmological context in which reionization is embedded. I will conclude with some important future directions of research.

Oct. 24, Tuesday 1:10 pm
Ardis Eliasdottir, Niels Bohr Institute
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Extinction Curves of Lensing Galaxies"
Dust extinction causes light from distant sources to be dimmed on its way to the observer. In cosmological studies, such as SN Ia studies, it is of great importance that the effects of dust extinction be correctly accounted for. However, although dust properties, and hence extinction, are expected to vary with redshift, not very much is known about the extinction properties of high redshift galaxies. This is because the methods traditionally used to study extinction curves are only applicable for the most nearby galaxies. Studying gravitationally lensed quasars is an emerging method of studying the dust extinction of high redshift galaxies. I will present an ESO VLT study of 10 such lensing galaxies, with redshifts up to 1. The 10 systems display varying amount and type of extinction, with the doubly imaged quasar B1152+199 showing the greatest extinction with A(V)=2.4 and R_V=2.1 for a Galactic type extinction law.

Oct. 25, Wednesday 12:10 pm (Wed. Theory Lunch)
Sherry Suyu, CalTech
501 Campbell Hall
"Pixellated Potential Reconstruction in Gravitational Lensing"
Strong gravitational lensing can be used to determine cosmological parameters. B1608+656 is a quadruply imaged gravitational lens system with an extended source intensity distribution and two interacting galaxy lenses. This system is unique in that the three relative time delays between the four images were measured accurately with errors of only a few percent. In order to use such a system to determine the Hubble constant, one needs to model accurately the lens potential and the source intensity distribution. Since the lenses are two interacting galaxies, they are unlikely to be well described by simple parametric lens models. I will present a method to reconstruct perturbatively and iteratively the lens potential and source intensity distribution on grids of pixels. Our goal is to measure the Hubble constant accurately by reconstructing the lens potential such that its accuracy is solely limited by the noise in the data.

Oct. 31, Tuesday 1:10 pm CANCELLED
Juerg Diemand, UCSC
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Formation and evolution of CDM halos and their substructure"
Massive supercomputer simulations now allow to follow the formation and evolution of CDM halos and their subhalo population in detail. We have recently completed the "Via Lactea" run: It resolves a Milky Way scale halo with over 200 million particles, over ten times more than the previous largest run. It resolves over 10'000 subhalos, some inside the solar circle, many sub-subhalos and the mass in substructure has still not converged, i.e. it is growing with better numerical resolution. This wealth of small scale structure has implications for direct and indirect dark matter detection, stellar streams, disk heating, gravitational lensing and the Local Group dwarf galaxy population (the "missing satellites problem").

September 2006:
Sep. 5, Tuesday 1:10 pm
David Wittman, Davis
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Shear-Selected Clusters and Cosmic Shear from the Deep Lens Survey"
I present preliminary results from the Deep Lens Survey (DLS), a deep 20 square degree BVRz' imaging survey. First, I present the first sample of galaxy clusters selected based on their gravitational lensing shear rather than on any emitted light. The properties of this sample are being compared with those of X-ray and optically selected samples to explore possible biases in the different selection methods. Understanding such potential biases will be important for future large surveys which will use clusters to constrain cosmological parameters, as well as for understanding clusters as astrophysical laboratories in their own right. Second, I present work in progress on characterizing the redshift evolution of cosmic shear (weak lensing by large-scale structure). This effect is slated to be a cornerstone of cosmological constraints from future large surveys, but is only now being detected. I will give an observer's perspective and present some preliminary results.

Sep. 8, Friday 12:00 noon, INPA Journal club
Mike Boylan-Kolchin, Berkeley
LBNL 50-5026 (INPA conference room)
"Black holes and the assembly of massive galaxies"
I will discuss current ideas about the formation and evolution of massive galaxies and their central supermassive black holes. Many of these theories have been strongly influenced by the latest generation of numerical simulations, which are a powerful tool in helping us understand how galaxies evolve in merger events and how black holes (significantly) affect the properties of merger remnants. While mergers of gas-rich disk galaxies are thought to lead to the formation of elliptical galaxies, recent observational evidence suggests that merging of (gas-poor) elliptical galaxies is also an important process for galaxy evolution and for building up the most massive galaxies in the universe. I will present results of simulations of these mergers and argue that the large scale structure of dark matter plays an important role in producing observed properties of massive elliptical galaxies. These results also have important implications for the masses of the most massive black holes in the universe: I will suggest that standard estimates are likely too low, perhaps by up to a factor of three.
Sep. 12, Tuesday 1:10 pm
Gregory Rudnick, NOAO
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"The Mean Spectral Energy Distribution and Stellar Mass Density of Luminous Galaxies at z < 3"
We are rapidly gaining insight about the characteristics of high redshift galaxies, e.g. their star formation rates, stellar masses, ages, and morphologies. Concurrent with this rapid advance, however, it has become clear that traditional color-selection techniques provide a biased view of the high redshift Universe. This not only complicates placing the high redshift galaxies in a proper evolutionary context, but also makes it difficult to perform consistent comparisons with state-of-the art models of galaxy formation. For example, it is only now becoming apparent which galaxies at high redshift dominate the stellar mass and star formation rate budgets and how these galaxies are related. To obtain a comprehensive view of galaxy evolution, it is clear that it is necessary to select galaxies in a way that minimizes possible bias and over large enough area to mitigate the effects of field-to-field variance. I will present my measurements of the evolution in the volume averaged properties of the rest-frame optically selected galaxy population at z<3, determined from four disjoint deep fields with optical/Near-infrared wavelength coverage. I will discuss the volume averaged spectral energy distribution (SED) of rest-frame optically luminous galaxies and how the SED allows us to calculate the average stellar mass-to-light ratio of the luminous galaxy population as a whole. I then use this information to determine the evolution in the stellar mass density in luminous galaxies, which I consistently compare to theoretical models. I also will discuss the contributions to the mass budget made by different high redshift galaxy populations.

Sep. 14, Thursday 4:00 pm (Astronomy Colloquium)
Tony Tyson , UC Davis
2 Le Conte Hall
"A new look at the optical universe"
Wide fast and deep imaging of the sky will provide a new view of the optical universe. LSST will open time-volume space by three orders of magnitude over current facilities. Each field of the sky will be imaged 2000 times in six bands from the UV to near IR. The resulting shapes and photometric redshifts of billions of galaxies enables multiple precision probes of dark energy. The status of the LSST project will be reviewed.

Sep. 15, Friday 12:00 noon, INPA Journal club
Brian Gerke, Berkeley
LBNL 50-5026 (INPA conference room)
"Galaxy Groups in DEEP2: Implications for cosmic evolution"
Groups and clusters of galaxies, as the largest, most recently formed objects in the universe, carry much information about the recent history of the cosmos. By studying these systems at a variety of epochs, it is possible to reconstruct both the evolution of clusters and the history of large-scale structure formation. Such studies provide important constraints on theories of galaxy formation and on cosmological parameters. With the recent completion of the DEEP2 Galaxy Redshift Survey at z~1, it is now possible to perform detailed studies of galaxy groups and clusters over a wider redshift range than ever before. In this talk I will present recent results suggesting that, at the DEEP2 epoch, galaxy groups had only recently become suitable environments for shutting off star formation in galaxies. I will also present evidence that DEEP2 groups are underluminous in the X-ray band, when compared with local systems. Finally, I will describe an ongoing project to compare the DEEP2 group population to the local sample detected in the 2dFGRS. This work will allow new tests of galaxy-formation theory by probing evolution in cluster mass-to-light ratios. It will also permit new constraints on cosmological parameters by measuring the evolution of the group abundance between z~1 and the present day; in particular, this study should provide the first-ever constraint from cluster counts on the dark energy equation of state parameter.

Sep. 18, Monday 12:10 pm (TAC seminar)
Ue-Li Pen, CITA
544 Campbell Hall
"The rise and fall of hydrogen"
The 21cm emission of hydrogen is in principle detectable throughout the visible universe after recombination. In practice, only low redshift hydrogen has been found and mapped. We review our theoretical understanding of the history of neutral hydrogen from reionization through today, and current efforts to open a new window on the universe through the 21cm line. If a new generation of low frequency telescopes succeeds, it will enlarge the mapped redshift volume of the universe by several orders of magnitude, and result in precision determination of dark energy and cosmological parameters.

Sep. 19, Tuesday 1:10 pm
Houjun Mo, U Mass Amherst
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Establishing the relationship between galaxies and dark matter halos"

Sep. 20, Wednesday 12:10 pm (Wednesday lunch)
Reinhard Genzel, UCB and MPE
544 Campbell Hall
"Spatially Resolved Galaxy Kinematics at z~2-3"
I will discuss recent results of carrying out sub-arcsecond studies of the gas kinematics in several z~2-3 samples of star forming galaxies. I will also show the first ~0.15" adaptive optics imaging spectroscopy of such a system. To our great surprise we find evidence for large disk galaxies already in place 2-3 Gyrs after the Big Bang.

Sep. 21, Thursday 4:10 pm (Astronomy Colloquium)
Ludovic van Waerbeke , UBC
2 Le Conte Hall
"Progress in Weak Lensing by Large Scale Structures: from CFHTLS to SNAP"
I will review the present status of weak lensing by large scale structures, how we got there, and discuss the road map for future projects like SNAP. I will emphasize some of the problems that will have to be solved before cosmic shear deserves the "high precision cosmology tool" label.

Sep. 25, Monday 12:10 pm (TAC seminar)
John Wise, Stanford
544 Campbell Hall
"Resolving the Formation of Protogalaxies" [ Movies ]
Numerous cosmological hydrodynamic studies have addressed the formation of galaxies. Here we expand the standard model of galaxy formation to include molecular hydrogen cooling and primordial stellar feedback with a suite of cosmological Eulerian adaptive mesh refinement simulations that resolve the Jeans length by at least 16 cells. We gradually introduce molecular hydrogen cooling, radiative transfer, metal enrichment, and radiative backgrounds to determine the importance of each process. In simulations that consider the standard galaxy formation model with only hydrogen and helium cooling, gravitationally unstable central objects with masses more than 105 solar masses within a radius of 1 pc form within dark matter halos ~108 solar masses. These cores do not fragment down in sub-solar scales and could form a massive black hole. We also observe that no rotationally supported disk forms before this central collapse. Then we introduce molecular hydrogen cooling while suppressing the residual electron fraction in order to restrict our focus to protogalaxies. Here protogalactic halos with masses greater than ~8 x 106 solar masses at z ~ 20 can cool and collapse. Due to the exponential nature of Press-Schechter formalism, this corresponds to an order of magnitude increase in protogalaxy number density at z = 20, and galaxy formation may start earlier than previously thought. Next we consider radiative feedback from primordial stars using time dependent adaptive ray tracing that is solved self-consistently with the hydrodynamics, chemistry, and radiative cooling. This technique retains the time derivative and is photon conserving. We follow more than 20 primordial stars as they photo-ionize their host halos and the surrounding few kpc and expel all baryons from their dark matter halos. The increased electron fraction in the relic HII regions of primordial stars causes molecular hydrogen to become more abundant and increases the number of primordial stars by a factor of a few. The dynamical and thermal feedback from primordial stars affect the protogalaxy in several ways, e.g. decreasing the baryon content, skewing the angular momentum distribution to higher values, increasing the temperature of accreting gas, and enriching the IGM with the first metals. Our results highlight the importance of the inclusion of primordial stars and molecular hydrogen cooling in high redshift galaxy formation models.

Sep. 26, Tuesday 1:10 pm
Shirley Ho, Princeton
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Next Frontiers of CMB: ISW and KSZ"
The Cosmic Microwave Background has been providing us with a wealth of information for cosmology. Here, we are going to present the next frontiers of the CMB: the Integrated Sachs-Wolfe Effect and Kinetic Sunyaev-Zeldovich effect.
In order to understand the evolution of the gravitational potential, we make use of the ISW effect via the following datasets: WMAP, 2MASS, SDSS photometric LRGs and Quasars and NVSS. We will discuss our methodologies, analysis and preliminary results.
To understand the evolution of electron density of the universe, we utilize the kinetic SZ signature of the CMB. This method is very promising with the upcoming surveys such as ACT and APEX, as long as we have a galaxy survey such as ADEPT or Panstarrs available. We will present our prediction for ACT cross ADEPT correlation and results of the application of this method to the WMAP and SDSS main spectroscopic galaxy sample as a trial example.

Sep. 27, Wednesday 12:10 pm (Theory Lunch)
Jun Zhang, UCB
501 Campbell Hall
"Linear Perturbation Theory of Inhomogeneous Reionization"

Sep. 28, Thursday 4:10 pm (Astronomy Colloquium)
Piero Madau, UCSC
2 Le Conte Hall
"Cold dark matter substructure in galaxy halos"
I will present initial results from "2e8MW", the highest resolution simulation to date of Galactic cold dark matter substructure. The run was recently carried out on NASA's Project Columbia supercomputer, and resolves the virialized volume of a redshift 0 galaxy host with nearly 100 million particles. It follows the formation and evolution of a Milky Way-size halo of mass 1.8e12 M_sun in a WMAP 3-year cosmology, using a total of 234 million dark matter particles to simulate the entire galaxy forming region.

August 2006:
Aug. 10, Thursday 1:10 pm
Stephon Alexander, Penn State
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Parity Violation in General Relativity and the WMAP Alignment Anomalies"
It has been argued by a number of researchers that the CMB data has low multipole anomalies. At this stage there are three physical explanation: systematics, astrophysical or cosmological. In this informal talk, I will argue that if parity violation is incorporated into general relativity then the alignment anomaly has a natural explanation in the context of inflation.
Aug. 15, Tuesday 1:10 pm (joint with TAC)
Andreas Burkert, Munich
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"SAURON's Challenge of the Major Merger Scenario of Elliptical Galaxy Formation"
Early-type galaxies are believed to form when galaxies of roughly equal mass collide and merge. I will summarize the results of recent numerical major merger simulations that indeed are very successful in explaining the observed PROJECTED structural and kinematical properties of early-type galaxies.
Recently integral field spectroscopy provides interesting new insight into structure of ellipticals. SAURON is one of these projects. Integral field spectroscopy for the first times makes it possible to determine the INTRINSIC structure of ellipticals applying Schwarzschild models. I will focus on the results obtained by the SAURON team which are very puzzling and a serious challenge for theoretical models. It turns out that the SAURON results cannot be reproduced by major merger models. Mergers are in general too chaotic to generate the tight correlations between rotation and anisotropy that are predicted by the Schwarzschild analyses. Either state-of-the-art Schwarzschild models are not sophisticated enough in order to provide useful information about the intrinsic properties of galaxies are other processes besides major mergers play a dominant role in shaping early-type galaxies.

Cosmology Seminars in Previous Years

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