Seminars of possible interest to people in the Berkeley Cosmology Group

Note that there are also other talks which generally might be of interest, including

July 2004:

July 20 (Tuesday) 12:30 pm
501 Campbell Hall
Bring your lunch and come ready to talk about cosmology (including recent papers, work, meetings attended etc.). People who went to the Santa Fe workshop and/or the Aspen galaxy formation meeting will bring science gossip.

Jul 21 (Wednesday) 12:10 pm
Guinevere Kauffmann , MPA
501 Campbell Hall
"Accretion onto black holes: the SDSS perspective"

Jul 26 (Monday Lunch) 12:10 pm
Simon White and Guinevere Kauffmann , MPA
501 Campbell Hall

Jul 28 (Wednesday) 12:10 pm
Simon White , MPA
501 Campbell Hall
"Simulation Input for Gravitational Lensing Studies"

Jul 29 (Thursday,RAL seminar) 4:00 pm please note time change
Ron Ekers, (CSIRO/ATNF)
544 Campbell Hall
"Dark Energy with an SKA pathfinder"
One of the key science goals for the SKA is to explore the large scale structure in the universe by extending HI surveys to high redshift. It has recently been realised that technology developments may now make it possible to obtain very large fields of view and hence to extend HI surveys to the whole visible sky at redshifts >1. This opens the possibility of a very clean measurement of dark energy in the universe by accurately delineating the small-amplitude "acoustic oscillations" in the power spectrum of the spatial distribution of HI emitting galaxies. The method is so powerful that a test may be possible with an SKA pathfinder telescope long before the SKA is realised. The full SKA will be able to explore any evolution of the equation of state of dark energy with time.

June 2004:

June 1 (Tuesday) 12 noon
Bruce Bassett , Oxford
LBNL, Bldg. 50, room 5026 (the INPA common room)
"Quo Vadis Dark Energy?"
The next ten years will arguably mark the high-point of observational cosmology. By comparing our current knowledge of cosmology and dark energy properties with expectations on a 2015 timescale it is clear that dark energy will provide a unique window into physics at very high energies and may even make string theory an experimentally testable science.

June 1 (Tuesday) 2:10 pm
Allan Adams , Harvard
Oppenheimer Room, CAMPUS (4th floor Birge Hall)
"LISA in the Sky with Dark matter (and other fun with mirrors)"

June 8 (Tuesday) 12:30 pm
501 Campbell Hall
Bring your lunch and come ready to talk about cosmology (including recent papers, work, meetings attended etc.). Martin will discuss the science project of the Blanco Dark Energy survey. (note, this is a 5Mb powerpoint file!!)

June 10 (Thursday) 4 pm
"Quantum Universe" discussion
LBL Building 50 Auditorium (note change!)
Persis Drell, Steve Kahn, and Andy Albrecht discussing the "Quantum Universe" report from HEPAP.

June 14-25, LBNL
Baryon Oscillations summer visitor program

June 15 (Tuesday) 12:30 pm
Informal seminar: Eliot and Todd
501 Campbell Hall
Bring your lunch and come ready to talk about cosmology (including recent papers, work, meetings attended etc.). Eliot and Todd will discuss their recent work on feedback and galaxy formation, astro-ph/0406070.

June 22 (Tuesday) 12:30 pm
501 Campbell Hall
Bring your lunch and come ready to talk about cosmology (including recent papers, work, meetings attended etc.).

June 29 (Tuesday) 12:30 pm
501 Campbell Hall
Bring your lunch and come ready to talk about cosmology (including recent papers, work, meetings attended etc.).

May 2004:

May 4 (Tuesday) 2:10 pm
544 Campbell Hall

May 6 (Thursday) 12 pm
Eric Linder, LBNL
50-5026 (INPA Conference Room)
"Dark Energy in the Next Generation"

May 11 (Tuesday) 2:10 pm
Vy Tran, ETH
544 Campbell Hall
Linking Star-forming Galaxies to Passive Systems: The Post-Starburst Connection
We isolate post-starburst (E+A) galaxies at intermediate redshifts (0.3 < z < 1) to understand how star-forming galaxies evolve into passive, early-type systems in both the cluster and field environment. We find E+A's make up a significant fraction (~11%) of the cluster galaxy population at z>0.3, and that >30% of early-type members have undergone an E+A phase by z~0. We also find evidence in clusters of a decreasing characteristic E+A mass with redshift, similar to the decrease in luminosity of rapidly star-forming field galaxies since z~1 (``down-sizing''). In comparison, only ~3% of field galaxies at intermediate redshifts are E+A's. Although the E+A fraction in the field is lower than in clusters, the E+A phase is still an important link between emission line galaxies and absorption line systems in this environment: we estimate that ~25% of passive galaxies in the local field had an E+A phase at z<1.

May 16-18 (Sun-Tuesday)
Wide Field Meeting, LBL
A conference on Wide-Field Imaging From Space will be held May 16-18, 2004 at the Lawrence Berkeley National Laboratory. The conference will focus on the scientific opportunities afforded by wide-field imaging from space in the optical and near-infrared.

May 18 (Tuesday) 2:10 pm
Avishai Dekel , Hebrew University and UC Visiting Miller Prof
544 Campbell Hall
"The Origin of Dwarf Galaxies and Dark-Dark halos"

May 28 (Friday) 12 noon
Ben Gold , UC Davis
LBNL, Bldg. 50, room 5026 (the INPA common room)
"Looking for Dark Energy in ISW Correlations"
The integrated Sachs-Wolfe (ISW) effect is a secondary CMB signal normally buried beneath the primary one. Its dependence on the evolution of the gravitational potential makes it a tantalizing candidate for a different way of seeing the effects of dark energy. One technique for extracting more information from the ISW effect is to look for correlations between CMB maps and other observations dependent on structure along the line of sight. Here I will discuss correlating the CMB with galaxy number counts and CMB lensing maps, and what future observations of this type could reveal about dark energy.

April. 2004:

Apr. 1 (Thursday) 4:00 pm (Astronomy Colloquium)
Ann Zabludoff, Arizona
1 Le Conte Hall
"The Roles of Environment in Galaxy Evolution"
What is the evidence that environment affects galaxy evolution in the nearby Universe? Which environments and environmental mechanisms are the most influential? How might we expand our knowledge to higher redshifts? I will discuss results from recent surveys of rich clusters, poor groups, and the field at z~0 that shed some light on these issues and that raise others.

Apr. 2 (Friday) 1:30 pm
Dennis Zaritsky, Arizona
544 Campbell Hall
"Spinoffs From the Las Campanas Distant Cluster Survey"
I will briefly describe the Las Campanas Distant Cluster Survey (LCDCS), in which we identified ~1000 galaxy cluster candidates at 0.35 < z < 1 as low surface brightness fluctuations in the sky from drift-scan images obtained at the Las Campanas 40-inch telescope. Subsequently, I will focus on three areas (1) strong lensing by high-redshift clusters, (2) H-alpha emission line measures of the current star formation rates of cluster galaxies at z ~ 0.8, and (3) preliminary results from the ESO Distant Cluster Survey (EDisCS), which involves intensive follow-up observations of ~ 20 LCDCS clusters.

Apr. 6 (Tuesday) 2:10 pm
Chris Hirata, Princeton
544 Campbell Hall
"Weak Lensing of the CMB by Large-Scale Structure"
Weak gravitational lensing of the cosmic microwave background is a potentially valuable probe of the distribution of matter in the universe. The talk will present an overview of this cosmological probe, including statistical methods, current attempts to detect the effect, and future prospects.

Apr. 6 (Tuesday) 4:00 pm (LBL RPM)
David Schlegel, Princeton
Building 50B, Room 4205, LBNL
"The Galaxy Power Spectrum on the Largest Scales and the Hunt for Baryon Oscillations"
Apr. 7 (Wednesday), 12:10 pm (TAC seminar)
Renyue Cen, Princeton
501 Campbell Hall
Cosmological reionization

April 7 (Wednesday ) 5:45 pm
Wendy Freedman, Carnegie
155 Dwinelle Hall
Regents Lecture:
New, large, ground and space telescopes are contributing to an exciting and rapid period of growth in observational cosmology. The subject is now far advanced from its early days of being data-starved and unconstrained, and new data are fueling a healthy interplay between observations and experiment and theory. I will touch on a number of areas in cosmology: measuring the expansion rate of the universe or Hubble constant, the amount of mass in the universe (ordinary and dark), and the cosmological constant or dark energy component, that is causing the universe to speed up its expansion.

Apr. 8 (Thursday) 4:00 pm (Astronomy Colloquium)
Alan Dressler, OCIW
1 Le Conte Hall
"IMACS on Magellan: The Instrument and its Science"
Alan Dressler led the team that built the Inamori-Magellan Areal Camera and Spectrograph for the Magellan Baade 6.5-m telescope. He will discuss aspects of the design, construction, and performance of this wide-field, multipurpose instrument. Dressler will also describe some of its current science programs, including his own work on galaxy evolution in clusters, and the IMACS Deep Survey, a much-expanded version of the Gemini Deep-Deep Survey.

April 12 (Monday) 12:10 pm (Monday Lunch)
Wendy Freedman, Carnegie
501 Campbell Hall

April 12(Monday ) 4:30 pm (Physics Colloquium)
Wendy Freedman, Carnegie
1 LeConte Hall
"Measuring Cosmological Parameters"
Recent measurements have led to a concordance model in cosmology, with a universe that has a Hubble constant of 72 kilometers/second/Megaparsec, and which is geometrically flat, with one third of the matter-energy density in matter, and two thirds in attributed to a dark energy component. I will discuss recent results in a number of areas in cosmology, focussing primarily on the current expansion rate of the universe (the Hubble constant), and the cosmological constant or dark energy component.

April 13 (Tuesday)
Seminar moved to Monday Lunch (see above),
12 noon 501 Campbell Hall

Apr. 20 (Tuesday) 2:10 pm
John Dubinski, CITA/U Toronto
544 Campbell Hall
A Universe in Motion: The Dynamical Evolution of Galaxies in a Cosmological Context
Interactions and mergers drive galaxy morphological evolution. The recent convergence of the cosmological paradigm the past few years allows a detailed quantitative examination of the dynamical evolution of galaxies in the cosmological context. Some key issues are understanding the merger rate and its importance for the development of the ellipticals and their scaling relations, the dependence of morphology on galactic environment and the formation of galaxy clusters, their giant central ellipticals and the recently discovered distribution of intracluster stars. Simulations of galaxy mergers reveal both grace and violence that creates a complex, distribution of shells, loops and ripples that lies just below the threshold of the deepest images. Simulations of clusters clearly demonstrate the formation of giant ellipticals and surrounding smaller ellipticals embedded in the spray of intracluster stars.

Apr. 21 (Wednesday), 12:10 pm (TAC Seminar)
Lam Hui, FermiLab
501 Campbell
"The Small Scale Structure Frontier"
As microwave background observations and galaxy surveys begin to pin down the large scale structure of the universe, I will describe efforts to measure and interpret small scale structure. I will discuss examples from the intergalactic medium, lensing and the relevance for inflation.

Apr. 22 (Thursday) 4:10 pm (Astronomy Colloquium)
Avishai Dekel, Hebrew University
1 Le Conte Hall
"The Characteristic Scale of Galaxy Formation"
Recent data, e.g. from SDSS and 2dF, reveal a robust bi-modality of the galaxy population, which is divided into two major classes at a characteristic stellar mass of M_* ~3x10^{10} Msun (near L_*). Less massive galaxies tend to be blue, star-forming disks residing in low-density environments. Their properties are correlated along a "fundamental line" of decreasing surface brightness, internal velocity and metallicity with decreasing luminosity down to the smallest dwarf galaxies. Galaxies above the critical mass are dominated by spheroids of red, old stars, with high surface brightness and metallicity independent of luminosity. They tend to reside in high-density environments and to host AGNs. It will be shown in simple terms how this bi-modality and critical scale can arise as the combined imprint of three different physical processes. In galaxies below the critical mass, the stellar disks are built by cold flows, with supernova feedback regulating star formation and driving the fundamental line. In galaxies above the critical mass, the infalling gas is heated by an extended shock to the dark-matter halo virial temperature. This hot, dilute gas is vulnerable to AGN feedback, which prevents it from ever cooling to form stars. Galaxies near the critical mass are thus the most efficient star formers, yielding a minimum in the halo mass-to-light ratio at the same critical scale. The implications on galaxy-formation modeling will be discussed, and the main discrepancies between theory and observation will be addressed in view of these new ideas.

April 26 (Monday) 12:10 pm (Monday Lunch)
Mike Norman, UCSD
501 Campbell Hall
"Radiative and Chemical Feedback of the First Stars"

Apr. 27 (Tuesday) 2:10 pm
Henk Hoekstra, CITA
544 Campbell Hall
Nature's own weighing scales: measuring masses using weak gravitational lensing
For several decades observations have indicated that galaxies and clusters of galaxies are overweight. Unlike many humans, these structures in the universe have been able to hide their obesity because the excess weight is in the form of dark matter, which does not emit any detectable radiation. Fortunately, nature has provided us with a technique that allows us to weigh these objects directly, without having to make assumptions about the dynamical state or orientation. In this talk I will introduce the basics of this technique, weak gravitational lensing, and demonstrate its unique use to measure the masses from galaxies, galaxy groups, clusters of galaxies and superclusters. Having accurate masses for these systems is important for our understanding of their formation and the complex astrophysics involved. In addition, the abundance of clusters can be used as an sensitive probe of the cosmological world model, provided accurate masses are available.

Mar. 2004:

Mar. 1 (Monday Lunch) 12:10 pm
Mattias Steinmetz, Potsdam
501 Campbell
informal update/discussion

Mar. 2 (Tuesday) 2:10 pm
Lori Lubin, UC Davis
544 Campbell Hall
"High-Redshift Clusters of Galaxies : Understanding Structure Formation and Galaxy Evolution"
Clusters of galaxies provide a powerful probe of the nature of galaxy formation and the origin of structure in the Universe. Using a variety of techniques, most notably optical and X-ray selections, clusters of galaxies can now be routinely detected at redshifts up to 1 and even beyond. In this talk, I present our results on a continuing study of optically-selected clusters at redshifts of z > 0.6. The global cluster properties, such as dynamics and X-ray/optical relations, will be presented in the context of cluster formation timescales and evolutionary histories. In addition, I will examine the cluster galaxy populations, focusing on their colors, spectral characteristics, ages, and morphological classifications. I will discuss the implications of these data on the evolution of the cluster galaxies, the origin of galaxy morphologies, and the process of cluster formation from z = 1 to the present.

Mar. 3 (Wednesday), 12:10 pm (TAC seminar)
Tzu-Ching Chang, UCB
501 Campbell
"Weak Lensing Measurement with the FIRST Radio Survey"

Mar. 9 (Tuesday) 2:10 pm
Steve Furlanetto, CalTech
544 Campbell Hall
"Observing Neutral Hydrogen In the Reionization Epoch"
There has recently been an explosion of interest in the processes that reionize the intergalactic medium (IGM). Existing observational constraints from the cosmic microwave background and high-redshift quasars indicate that the ionization history is significantly more complex than previously thought, containing a rich set of information about the first generations of luminous sources and the IGM. I will describe how observations of 21 cm emission and absorption by neutral hydrogen at high redshifts can help to resolve these questions. These measurements offer the opportunity to answer a large set of questions that are otherwise inaccessible to us. In particular, they will allow us to measure the detailed time history of reionization, the morphology of the phase transition between a neutral and ionized IGM, and the matter power spectrum at z~15. I will also discuss some of the (many) observational challenges that must be met in order to measure the 21 cm signal as well as some strategies to overcome these difficulties.

Mar. 15 (Monday Lunch) 12:10 pm
Avishai Dekel, Hebrew University
501 Campbell
Phase-Space Structure of Dark Halos

Mar. 16 (Tuesday) 2:10 pm (joint seminar with particle group)
Dan Chung, U Wisconsin
544 Campbell
"Hawking Radiation in Odd Spacetime Dimensions"

Mar. 23 (Tuesday) 2:10 pm
Risa Wechsler, U Chicago
544 Campbell
"Connecting Galaxies & Clusters to their Dark Matter Halos"
Although the distribution of dark matter and the properties of dark matter halos as a function of cosmology are now fairly well understood, the detailed connection between observable galaxies and their dark matter host halos is much less certain. Understanding this connection is essential for making full use of large cosmological data sets, like the distribution of galaxies and clusters in the Sloan Digital Sky Survey (SDSS). Much of this connection can be understood with pure gravitational physics: the spatial clustering properties of dark matter halos, combined with simple assumptions about the luminosities and colors of the galaxies they host, can reproduce those of SDSS galaxies. Understanding this connection is also essential for making full use of the largest ever sample of galaxy clusters, those identified in the SDSS -- the abundance of massive clusters is a powerful discriminator between cosmologies, but only if the observable properties of these clusters can be closely connected to halo mass. Advances in cluster finding techniques, combined with large mock galaxy catalogs that match the relation between galaxy luminosity, color, and environment, now make this possible with optical data. I show how these catalogs can be used to calibrate cluster finding techniques and to make direct predictions in observational space, and how a combination of mass measurements and clustering statistics can be used to constrain the cluster mass scale and put constraints both on cosmology and on the relation between galaxies and dark matter halos.

Mar. 30 (Tuesday) 2:10 pm
Ben Metcalf, UCSC
544 Campbell Hall
"Small-Scale Structure, Missing Galaxies and Gravitational Lensing"
I will review resent work, both theoretical and observational, on measuring the abundance of small scale structures in the dark matter distribution using gravitational lensing. The cold dark matter model predicts that there is a large number of invisible clumps of dark matter in galactic halos and intergalactic space. Strong evidence for these structures and constraints on their abundance and size are coming from the new method of spectroscopic lensing.
Mar. 31 (Wednesday), 12:10 pm (TAC seminar)
Gil Holder, IAS
501 Campbell Hall
"Microwave Foregrounds: Galaxy Clusters at cm/mm Wavelengths"
Galaxy clusters have unique signatures at microwave frequencies that can be useful tools for studying cosmology and astrophysics. The largest effect is the Sunyaev-Zeldovich effect (Compton scattering of CMB photons), but there are also distinct signatures due to gravitational lensing of the CMB and reflection of bright embedded radio sources. These effects have either been detected already or will likely be detected in the next few years, so I'll discuss some of the open questions that need to be addressed to use galaxy clusters as precise cosmological tools or as good laboratories for astrophysics.

Feb. 2004:

Feb. 2 (Monday) 12:10 pm
Alice Shapley, UCB
544 Campbell

Feb. 4 (Wednesday), 12:10 pm (TAC seminar)
Nick Gnedin, Colorado
501 Campbell
6 - 10 - 17
Cosmological reionization - the process of ionization of the bulk of cosmic gas by ultra-violet radiation from primeval galaxies - is by far the most dramatic event that has occurred in the universe since the formation of the first star. I will overview recent observational and theoretical progress (and regress) in our understanding of reionization, and will discuss the opportunities for Radio Astronomers to earn another Nobel Prize.

Feb. 5 (Thursday) 10 am
Denis Barkrats
375 Le Conte Hall
The CAPMAP experiment

Feb. 5 (Thursday) 4:00 pm (Astronomy Colloquium)
Tommaso Treu, UCLA
1 Le Conte Hall
Clusters of Galaxies in a Hierarchical Universe: Dark Matter Halos and Environmental Processes.
The galaxy population of clusters is dramatically different from the galaxy population in the general field. The morphological mix in the cores of clusters is dominated by elliptical and lenticular galaxies as opposed to irregulars and spirals dominating the field environment. In addition, at any given morphological type, star formation is suppressed in the cluster environment. The differences could arise from interactions between galaxies, dark matter and hot inter-cluster medium.
I will present a comprehensive observational study of two galaxy clusters at intermediate redshift (0.4-0.5) over an unprecedented wide field of view (10 Mpc in diameter) extending from the core out to 2-3 virial radii. HST images are combined with extensive ground spectroscopy (~1000 redshifts) to determine the cluster mass distribution via weak-lensing analysis and the properties of cluster galaxies as a function of environment. The main aim of the analysis is to understand the build-up of clusters and their galaxy population, by focusing on the so far unexplored outskirts of clusters, where in-falling galaxies first hit the known cluster potential and the hot inter cluster medium.

Feb. 10 (Tuesday) 1:10 pm
Mike Gladders, OCIW
375 Le Conte
The red cluster survey

Feb. 17 (Tuesday) 1:10 pm
Hee-Jong Seo, Arizona
544 Campbell
"Probing Dark Energy with Baryonic Acoustic Oscillations from Future Large Galaxy Redshift Surveys"
In this talk, we will show that the measurements of the baryonic acoustic oscillations in large high redshift galaxy surveys offer a precision route to the measurement of dark energy. The cosmic microwave background provides the scale of the oscillations as a standard ruler that can be measured in the clustering of galaxies, thereby yielding the Hubble parameter and angular diameter distance as a function of redshift. This, in turn, enables one to probe dark energy. The talk will discuss about the importance of prospective spectroscopic redshift surveys upto z=3 to achieve the precision required, and will show the expected statistical errors on cosmography while marginalizing over a large number of cosmological parameters including a time-dependent equation of state. The talk will also cover the dependence of performance on redshift, survey conditions, fiducial model, and the redshift uncertainty. While the future supernovae program will provide excellent constraints on dark energy, we find that redshift surveys will offer a promising independent route to the measurement of dark energy.

Feb. 24 (Tuesday) 1:10 pm
Gus Evrard, U Michigan
544 Campbell
"Galaxy Clusters: Models and Mysteries"

Feb. 24 (Tuesday) 2:10 pm particle theory seminar
Stephon Alexander, Stanford
Oppenheimer Room, Birge Hall
"The Matter-Anti Matter Asymmetry from Inflationary Gravity Waves"

Jan. 2004:

Jan. 13 , 12:10 pm (special TAC seminar)
no talk

Jan. 14 , 12:10 pm (special seminar)
Josh Winn, CfA
544 Campbell Hall
"The central images of gravitationally lensed quasars: a new tool to study galaxy centers"
When a galaxy acts as a gravitational lens, theory predicts there should be an odd number of images. Yet almost all observed lenses have 2 or 4 images. The missing image is the "central" or "maximum time" image, which should appear close to the center of the foreground galaxy, and should be very faint due to de-magnification by the high density of material near the galactic core. I will present the most secure detection of a central image, and explain how the properties of central images can be used to constrain the central density of the lens galaxy and the mass of its central black hole. I will also discuss future prospects for discovering more central images and probing galactic cores at significant redshift.

Jan. 20 , 1:10 pm (special Astronomy talk )
no cosmology talk

Jan. 23, (Friday) , 12:10 pm
Doug Finkbeiner, Princeton
544 Campbell
"Microwave ISM Emission Observed with WMAP and Green Bank"
Microwave emission from H II regions in the Galactic plane is mostly free-free emission, but recent data indicate that the ISM emission outside of H II regions is dominated (at 14-30 GHz) by something OTHER than free-free, synchrotron, or thermal (nonmagnetic) dust emission. I will use the WMAP (Wilkinson Microwave Anisotropy Probe) data at high latitude to show that spinning dust is a possible explanation for the dust-correlated emission (assumed to be synchrotron radiation) seen by WMAP. Although synchrotron at high latitude cannot be ruled out using the WMAP observations, the claim by the WMAP team of an upper limit on spinning dust emission (Bennett et al. 2003) is incorrect.

In a separate analysis, I combine the Green Bank Galactic Plane Survey (|b| < 3 deg; 8, 14 GHz) with WMAP to rule out dust-correlated synchrotron as the dominant emission mechanism in the WMAP channels, and argue that spinning dust (Draine & Lazarian 1998) is a viable explanation. Planned observations with the GBT and other telescopes will help refine these spinning dust models. If spinning dust is common in our Galaxy, it could become a great diagnostic tool for studying the physical properties of the ISM.

Jan. 26, (Monday) , 12:10 pm
Henk Hoekstra, CITA
544 Campbell
"The hunt for the equation of state of the universe"
The recent discovery that the dynamics of the universe are dominated by some "dark energy" has created much excitement and puzzled physicists. Although many different mechanisms have been proposed to explain the results, current observational constraints to distinguish between various models are limited. The key parameter to be determined over the next decade is the equation of state w=P/rho, which relates the pressure and the energy density of the dark energy.

I will discuss several techniques that can be used to constrain this parameter. The type Ia supernovae and weak lensing measurements will use data from the upcoming CFHT Legacy Survey, whereas the RCS2 cluster survey uses the abundance of massive clusters to constrain cosmological parameters. To support the feasibility of these techniques I will discuss some recent results obtained using data from the RCS1 cluster survey.

Dec. 2003:

Dec. 2 (Tuesday), 1:10 pm
Arthur Lue, CWRU and CERN
544 Campbell Hall
"Braneworlds and Beyond: Can dark energy be modified gravity?"
The nature of the fuel that drives today's cosmic acceleration is an open and tantalizing mystery. I entertain the suggestion that the acceleration is not the manifestation of yet another new ingredient in the cosmic gas tank, but rather our first real lack of understanding of gravitational physics. I discuss first an intriguing braneworld model (Dvali-Gabadadze-Porrati) and extend the discussion to a more general context, addressing questions about modified gravity cosmologies, and allowing concrete distinctions to be made between modified gravity and dark energy at astrophysically-interesting, and even solar-system, scales, with these distinctions being subject to imminent observational discrimination.

Dec. 4 (Thursday), 3 pm
Vincent Reveret,
375 LeConte
"Development of large bolometer arrays at CEA-Saclay - Application to (sub)millimeter ground-based astronomy"
Astronomy in the 100 microns - 2 mm range is a really young science. The historical difficulties for observing in that band were principally due to the low sensitivity of detectors and the obligation to get rid of the atmospheric opacity and noise. Thereafter, satellites such as IRAS, COBE and ISO have revealed the far-infrared view of the Universe to astronomers. It appeared that many fundamental questions could be studied in the (sub)millimeter : CMB, evolution of galaxies or star formation process for example. In the last 10 years, a new generation of (sub)millimeter instrumentation has been developed for space missions (Sirtf, Herschel in 2007) and ground missions working in transparent atmospheric windows (Scuba, Mambo, Sharc, ALMA,...). Different groups have started to build large bolometer focal planes that will have the same impact on millimeter astronomy than CCD had on optical and infrared astronomy. After an introduction on submillimeter astronomy in general, I will present the development of new generation bolometer arrays at CEA-Saclay in France. The detectors, originally built for the Herschel/Pacs instrument, have been adapted to longer wavelengths and to the ground-based conditions with the help of a new technological process. I will detail the basic bolometer array made of 256 multiplexed pixels and show results of preliminary lab tests and simulations of observations with these arrays. A sensitivity (NEFD) of 10 mJy/Hz^2 has been estimated at 1,2mm on the IRAM 30m that enables this instrument to be a perfect complement to future space missions.

Dec. 5 (Friday), 12 noon ( INPA Journal Club)
Chung-Pei Ma, UCB
Bldg. 50-A, room 5026 (the INPA common room)

Dec. 9 (Tuesday), 1:10 pm
Niayesh Afshordi, Princeton
544 Campbell Hall
"Cross correlating the CMB with the large scale structure of the universe"
The fluctuations of the CMB at angles larger than a tenth of a degree are mostly of primordial nature. Cross-correlating these fluctuations with the observable tracers of matter (e.g. galaxies, clusters, or cosmic shear) gives us a unique way of extracting small secondary anisotropies that probe the low redshift universe. In this talk, I will discuss the dominant sources of the cross-correlation signal, i.e. ISW and thermal SZ. The ISW effect is seen on large angles and is a direct probe of the dark energy, while the thermal SZ effect dominates smaller angles and probes the hot gas inside galaxy clusters. I will describe the current observational status, as well as theoretical expectations for the detection of each signal.

Dec. 10 (Wednesday), 12:10 pm (TAC seminar)
Matias Zaldarriaga, CfA
501 Campbell
"Constraining the epoch of Inflation: an astronomer's view"

Dec. 16 (Tuesday), 2:10 pm
Sonia Paban, U Texas
Oppenheimer Room, CAMPUS (4th floor of Birge, 2 doors left of the main elevator.)
"The entropy of the Microwave Background and the Acceleration of the Universe"

Dec. 18 (Thursday), 12:10 pm (TAC seminar)
Joe Silk, Oxford
501 Campbell

Nov. 2003:

Nov. 4 (Tuesday), 1:10 pm (Cosmology Seminar)
Joe Hennawi, Princeton
544 Campbell Hall
"Two Talks for the Price of One:
Cross-Correlating the Kinetic Sunyaev-Zel'dovich Effect with Cosmic Shear
Close Pairs of Quasars in the Sloan Digital Sky Survey"

Secondary anisotropies of the CMB have the potential to reveal intricate details about the history of our universe between the present and recombination epochs. However, because the CMB we observe is the projected sum of a multitude of effects, the interpretation of small scale anisotropies by future high resolution experiments will be marred by uncertainty and speculation without the handles provided by other observations. I will discuss how cross correlating the CMB with an overlapping weak lensing survey will isolate the elusive kinetic Sunyaev-Zel'dovich Effect from secondary anisotropies generated at higher redshifts. In particular, if upcoming high angular resolution CMB experiments, like PLANCK/ACT/SPT, cover the same area of sky as current and future weak lensing surveys, like CFTHLS/SNAP/LSST, the cross correlation of cosmic shear with the kSZ effect will be detected with high signal to noise ratio, increasing the potential science accessible to both sets of surveys. For example, if ACT and a CFHTLS like survey were to overlap this cross-correlation would be detected with a total signal to noise ratio greater than 220, reaching 1.8 per individual multipole around l ~ 5000.
I will then completely change the subject and discuss the discovery of close pairs of quasars in the Sloan Digital Sky Survey (SDSS). The number of close < 60" quasar pairs is over two orders of magnitude larger than expected from extrapolations of the quasar correlation function to small scales. We have already nearly doubled the number of known close quasar pairs, and preliminary results will be highlighted. I will discuss observational strategies for finding close pairs and the manifold science motivations, including quasar clustering, the search for strong gravitational lensing by clusters of galaxies, and using close pairs of quasars to study the Lyman alpha forest.

Nov. 11 (Tuesday), 1:10 pm (Cosmology Seminar)
Subha Majumdar, CITA
544 Campbell Hall
"Future Cluster Surveys: Probing both Cosmology and Cluster Physics"
Upcoming high angular resolution and high sensitivity SZ cluster surveys would provide us with such a large sample of clusters that one can take a leap in the way one does cosmology with clusters. With a little care, one can not only try to do `precision' cosmology but can also take a closer look at cluster structure and evolution `at the same time'. In addition to cluster counts, the surveys would also give us the SZ power spectrum which has its own cosmological and gas physics dependences. By combining the two, one can have an additional handle on cluster physics.

Nov. 12 (Wednesday), 12:10 pm (TAC seminar)
Ariyeh Maller, U Mass
Large Scale Structure in the Two Micron All Sky Survey

The recently completed Two Micron All Sky Survey (2MASS) is the largest catalog of near infrared data, containing more than 500 million stars and 1.6 million extended sources. The near infrared offers us the opportunity to study galaxies in a band where dust obscuration is minimized and for which mass-to-light ratios vary the least. I will discuss large scale structure in 2MASS, focusing on the angular correlation function and the flux dipole we measure using 2MASS galaxies. The flux dipole is 16 degrees from the CMB velocity dipole, where this offset seems to be entirely due to the contribution of the few hundred brightest galaxies. From comparing the acceleration of the Local Group from the flux dipole with our motion with respect to the CMB I find that K-band selected galaxies are unbiased tracers of the mass distribution. I will show that the angular correlation function of 2MASS galaxies deviates significantly from a pure power law as expected in halo occupation models. Finally I will invert the angular correlation function to determine the power spectrum of K-band selected galaxies which is well fit by a CDM type power spectrum on linear scales.

Nov. 17 (Monday), 12:10 pm (Monday Lunch)
Ravi Sheth, U Pitt
501 Campbell Hall
Much ado about nothing
Galaxy surveys show the presence of large voids (characteristic radii about twenty megaparsecs). It is sometimes argued that the voids in the galaxy distribution are much too large to be easily accomodated in CDM models. To address this, I'll discuss a simple model of voids in the dark matter distribution, and what the model implies for the properties of void galaxies.

Nov. 17 (Monday), 2:30 pm Theoretical Physics Seminar
Neal Weiner, U Washington
LBNL 50A-5132
"Neutrino Mass and Dark Energy"

Nov. 18 (Tuesday), 1:10 pm (Cosmology Seminar)
Mariangela Bernardi, CMU
544 Campbell Hall
Early-Type Galaxies in the SDSS: evolution and environment
Galaxy formation remains one of the unsolved mysteries in cosmology. It is a complex process, involving both gravity and hydrodynamics, and can be complicated by such ingredients as turbulence, magnetic fields, black-hole formation and accretion, nuclear activity, tidal and merger interactions. Although the physics of disk formation has made considerable progress, we do not have a comparable understanding of spheroid formation. One way to quantify galaxy formation and evolution is to compare absorption lines measurements and colors with the prediction of stellar population synthesis models. I will show that using early-type galaxy observables extracted from the SDSS database I find: 1) strong evidence of differential evolution: galaxies with smaller velocity dispersions evolve more rapidly, which implies that smaller galaxies are also younger; 2) galaxies in different environments show little difference in colors and linestrengths; 3) stellar population synthesis models do not fit well the observations. These results combined with other findings from the SDSS allow for a sharp test of galaxy formation theory.

Nov. 20 (Thursday), 1:00 pm
David Spergel, Princeton
375 LeConte Hall
First year WMAP results

Nov. 25 (Tuesday), 1:10 pm (Cosmology Seminar)
Brad Benson, Stanford
544 Campbell Hall
"Latest Results from the Sunyaev-Zel'dovich Infrared Experiment (SuZIE)"
The Sunyaev-Zel'dovich Infrared Experiment (SuZIE) is a bolometeric receiver designed to observe the Sunyaev-Zel'dovich Effect (SZE) in distant (z>0.15) clusters of galaxies. SuZIE observes the SZE in three frequency bands at 145, 221, and 355 GHz, which allows a separation of the thermal and kinematic components of the SZE. The SuZIE observing program has so far measured the SZ spectrum towards 13 clusters of galaxies. I will discuss some observational challenges of measuring the spectrum of the SZE, review the science results from SuZIE, and briefly discuss the next generation SuZIE instrument.

Oct. 2003:

Oct. 6 (Monday), 3 pm ( RAL Seminar)
Chris Fassnacht, UC Davis
544 Campbell Hall
Measuring the Hubble Constant with Gravitational Lenses

Gravitational lenses can provide an elegant one-step measurement of H0 at cosmological distances. Although plagued by many years of controversy, this method is now producing exciting results. I will discuss recent measurements of time delays from lens systems, advances in lens modeling, and some new programs aimed at improving the data set for lens studies.

Oct. 7 (Tuesday), 1:10 pm
Kin-Wang Ng, UC Berkeley and Academia Sinica, Taiwan
544 Campbell Hall
Some Issues in CMB Interferometry

We will give a brief introduction to the AMiBA project, and then discuss some issues in CMB interferometry such as drift-scanning, real-space and uv-plane pixelization, E/B separation, and large-sky convolution.

Oct. 8 (Wednesday), 12:10 pm (TAC Seminar)
David Rusin, U Penn
501 Campbell Hall
The Structure and Evolution of Early-Type Galaxies: A Lensing Perspective

Gravitational lenses represent a unique sample of galaxies: they are mass-selected, dominated by early-type morphologies, and naturally span the redshift range 0 < z < 1. Moreover, the observed properties of lensed images are sensitive to the galaxy mass distribution, and the geometry provides a model-independent measurement of the projected mass. Lenses are thus powerful tools for investigating the structure and evolution of early-type galaxies. I will review recent progress on these fronts using individual lenses, and introduce statistical methods to constrain the radial mass profile in early-type galaxies, trace the evolution of their stellar populations, and address the relationship between luminous and dark matter on galaxy scales.

Oct. 14 (Tuesday), 1:10 pm (Cosmology Seminar)
Taotao Fang, UCB
544 Campbell Hall
"Probing the Warm-Hot Intergalactic Medium"
Cosmological simulations reveal the cosmic web structure of the universe, where moderately overdense filaments connect collapsed regions such as groups and clusters of galaxies. These filaments, named "Warm-Hot Intergalactic Medium", or "WHIM", account for a large amount of the so-called "missing baryons" and are shock-heated to temperatures between 10^5 - 10^7 K. I will discuss detailed imaging and spectroscopy studies of UV/X-ray properties the WHIM gas via cosmological simulations and observations. I will also talk about the correlation between X-ray and the large scale structure. Finally I will discuss the detectability with proposed X-ray telescopes.

Oct. 17 (Friday), 12 noon ( INPA Journal Club)
Alexandre Amblard, UCB
Bldg. 50-A, room 5026 (the INPA common room)
"Gravitational Lensing with APEX"

Oct. 21 (Tuesday), 1 pm (really 1:10 pm)
544 Campbell Hall
Discussion of papers
Come ready to discuss some recent cosmology papers. Suggestions welcome:
Statistics of Arcs in Giant Galaxy Clusters, Holder,Dalal and Hennawi, astro-ph/0310306

Oct. 22 (Wednesday), 12:10 pm (TAC seminar)
Volker Bromm, CfA
501 Campbell
Cosmic Renaissance: The First Sources of Light
How and when did the cosmic dark ages end? I present simulations of the formation of the first stars and quasars, discuss their feedback on the IGM, and describe ways to probe their signature with WMAP and JWST. The first supernovae are responsible for the initial metal enrichment of the IGM, and I address the impact of this initial enrichment event on the subsequent history of structure formation. Finally, I describe the properties and statistics of high redshift GRBs and SNe that result from the first generation of stars.

Oct. 28 (Tuesday), 1:10 pm (Cosmology Seminar)
Alice Shapley, UCB
544 Campbell Hall
"Star-forming galaxies from z~3 to the redshift desert"
We first present the results of detailed studies of the astrophysical conditions in z~3 Lyman Break Galaxies (LBGs), placing particular emphasis on what is learned from LBG rest frame UV spectra. By drawing from our database of ~1000 spectra, and constructing higher S/N composite spectra from galaxies grouped according to various parameters, we can show how the rest-frame UV spectroscopic properties systematically depend on other galaxy properties. Such information is crucial to understanding the detailed nature of LBGs, and their impact on the surrounding IGM. We then turn to a new survey of UV-selected star-forming galaxies at z~1.5-2.5, in the so-called ``redshift desert.'' Adjusting the z~3 LBG color criteria to find similar types of galaxies at z~2, and using a UV-optimized spectroscopic set-up, we have assembled nearly 700 galaxies spectroscopically confirmed to lie in this virtually unexplored, yet critical, period in the history of the universe. Ongoing and future work will probe the detailed astrophysical conditions in z~2 galaxies, including the nature of their stellar IMFs, stellar and interstellar metallicities, dynamical masses, stellar populations, and the properties of the large scale outflows which are characteristic of high-redshift star-forming galaxies. Differential comparisons with the z~3 sample will be important for studying the evolution of distant galaxies.

Oct. 29 (Wednesday), 12:10 pm (TAC seminar)
Oleg Gnedin, STSCI
501 Campbell
Formation of Globular Clusters in Hierarchical Cosmology
Numerical simulations of a Milky Way-sized galaxy demonstrate that globular clusters with properties similar to those observed can form naturally at z > 3 in the concordance LCDM cosmology. The clusters in our model form in the strongly baryon-dominated cores of supergiant molecular clouds. The first clusters form at z = 12, while the peak formation appears to be at z = 3-5. The zero-age mass function of globular clusters can be approximated by a power-law with the slope -2, in agreement with observations of young massive star clusters. The total mass of the cluster population is strongly correlated with the mass of its host galaxy, as well as with the local average star formation rate. The first clusters serve as important sources of ionizing radiation within their host galaxies and may lead to gamma-ray bursts and intermediate-mass black holes.

Oct. 30 (Thursday), 4:10 pm (Astronomy Colloquium)
Kurt Adelberger, OCIW
2 Le Conte Hall
"The Evolving Universe of Galaxies from Redshift 3.5 to 1.5"
In the past 7 years we have measured spectroscopic redshifts for nearly 2000 galaxies at redshifts between 1.5 and 3.5. This large sample has made it possible to characterize the properties of galaxies (shapes, sizes, luminosities, rotational speeds, spatial clustering, etc) during the first third of the universe's history. I will describe some of the highlights of our survey. Many of our survey fields were chosen to lie in front of bright background QSOs whose absorption spectra reveal the spatial distribution of various ions in the intergalactic medium. Much of the discussion will concern what we can learn about galaxy formation from the relative spatial distributions of galaxies and of intergalactic metals and hydrogen.

Sept 2003:

Sep. 9 (Tuesday), 1 pm (really 1:10 pm)
Alexandre Amblard and Chris Vale, UCB
544 Campbell Hall
Practice talks for Galaxy Cluster meeting

Sep. 12 (Friday), 1:30 pm
Dr. Wolfgang Rau, TUM, Garching
375 LeConte Hall
Search for WIMPs with CRESST: technique and recent results

Sep. 16 (Tuesday), 1 pm (really 1:10 pm)
544 Campbell Hall
Discussion of papers
Come ready to discuss some recent cosmology papers. Suggestions welcome (will be posted here).

Sep. 23 (Tuesday), 1 pm (really 1:10 pm)
544 Campbell Hall
Summary of Cluster meeting
People from the cluster meeting (Adrian Lee, Alexandre Amblard, Martin White +other volunteers) will tell the rest of us what transpired.

Sep. 30 (Tuesday), 1 pm (really 1:10 pm)
Masahiro Takada, U Penn
544 Campbell Hall
Non-Gaussian signatures in cosmic shear

August 2003:

Aug. 1 (Friday), 12 noon ( INPA Journal Club)
Dragan Huterer, CWRU
Bldg. 50, room 5026 (the INPA common room)
"CMB Windows on Dark Energy"

Aug. 8 (Friday), 12 noon ( INPA Journal Club)
Jason Rhodes, Caltech
Bldg. 50, room 5026 (the INPA common room)
"TBA"(on weak lensing)

Aug. 8 (Friday), 2 pm note time change!
Francisco Prada, IAC
501 Campbell Hall
"The Fundamental Line"
I will present the new correlation between the mass-to-light ratio and the mean metallicity for the satellites of the Local Group. This relation, together with their central surface brightness, defines a Fundamental Line (Prada & Burkert 2002) where metal-poor and low surface brightness dwarf galaxies are dark matter dominated while metal-rich high surface brightness systems will have a low M/L ratio. This fundamental line is independent of morphological type, among other global parameters, as their star formation history. I will discuss the different interpretations and future work to understand the origin of the fundamental line in the framework of galaxy formation.

Aug. 22 (Friday), 12 noon ( INPA Journal Club)
Jim Bartlett, College de France
Bldg. 50, room 5026 (the INPA common room)
"Cosmology with the SZ effect"

Aug. 29 (Friday), 12 noon ( INPA Journal Club)
Carlo Baccigalupi, SISSA/ISAS
Bldg. 50, room 5026 (the INPA common room)
"Dark energy news on CMB & non-linear structure formation"

Aug. 29 (Friday), 2:30 pm
Simona Mei, IAS, Orsay
544 Campbell Hall
Informal discussion on SZ surveys

Past Cosmology Seminars in 2002-2003 Academic Year

Past Cosmology Seminars in 2001-2002 Academic Year

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