Note that there are also other talks which generally might be of interest, including Cosmology Workshops and: Theoretical Astrophysics Center Seminars (Mondays, 12:10 pm, 544 Campbell) CADiE Campus-Astro Discussion Extravaganza, 4:30 pm, seminar room in interaction space of CTP, LeConte Hall 4th floor. Physics Dept. Colloquia (Mondays, 4:30 pm, 1 LeConte) RAL seminars (usually Mondays 3:10 pm, 544 Campbell) Tuesday astro-ph coffee (11:15 am, 6th floor lounge, Campbell) Tuesday and Thursday RPM's at LBNL (4 pm, 50A-5132) Wednesday astronomy theory lunch (12:10, 544 Campbell) INPA CANDi at LBL: Cosmology, Astrophysics, Neutrino Discussion (Wednesdays 3:30 pm) Astronomy Colloquium (4 pm Thursdays, room varies) INPA and Astronomy journal clubs (both Friday at noon, at LBNL and on campus respectively). Friday astro-ph coffee (11:15 am, 6th floor lounge Campbell) This week in particle theory talks on campus and at LBL

Nov. 2, Monday 12:10 pm (TAC seminar)
Alyson Brooks, Caltech
544 Campbell Hall
"The formation of Realistic Galaxy Disks"
Much progress has been made in recent years in forming realistic disk galaxies in fully cosmological simulations. I will highlight the necessity of both 1) a physically motivated prescription for star formation and feedback and 2) very high numerical resolution to achieve a successful model for the formation of disk galaxies. I will then present results from the first simulated bulgeless disk galaxy. Finally, I will present results from an L* disk galaxy that emphasizes the interplay of both gas accretion and feedback in creating disks, and in quickly reforming disks despite disruption in low z major mergers.

Nov. 3, Tuesday 1:10 pm
Molly Peeples, OSU
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Balancing Outflows and Gas Dilution: The Mass-Metallicity Relation at z=0"
The gas-phase oxygen abundances of star-forming galaxies are tightly correlated with the galaxies' stellar masses such that more massive galaxies are more oxygen-rich. Because oxygen is produced on relatively short timescales (~10 Myr), this so-called mass-metallicity relation is a sequence of oxygen depletion: low-mass galaxies are metal-depleted relative to the true nucleosynthetic yield rather than massive galaxies being preferentially enriched. Preferential metal-depletion can be caused by either diluting the gas (e.g., via higher accretion rates of pristine gas or by lower star-formation efficiencies) or by preferentially removing metals from low-mass galaxies via galaxy winds. I will use simple analytic arguments to show how the observed mass-metallicity relation implies the required balance between gas dilution and gas outflow. In order to reproduce the mass-metallicity relation in cosmological smoothed particle hydrodynamic (SPH) simulations, star formation feedback is required. The resolution of such simulations, however, demands that this feedback is not directly modeled; I will discuss how I am examining and clarifying the issues surrounding different SPH galaxy wind implementations.

Nov.6 , Friday 12:00 pm (INPA journal club)
Guido D'Amico, SISSA
LBNL 50-5026

I will study generic single-field dark energy models, by a parametrization of the most general theory of their perturbations around a given background, including higher derivative terms. In appropriate limits this approach reproduces standard quintessence, k-essence and ghost condensation. There are no general pathologies associated to an equation of state w_Q < -1 or in crossing the phantom divide w_Q = -1. Stability requires that, when w_Q < -1, dark energy behaves, on cosmological scales, as a fluid with a virtually zero speed of sound. Theoretical and stability constraints are summarized on the quintessential plane (1+w_Q) vs. speed of sound squared. Finally, I will discuss the effect of dark energy with a zero speed of sound on non-linear scales, by calculating the cluster mass function.

Nov.6 , Friday 3:00 pm (SSL colloquium)
Christian Reichardt,UCB
SSL Addition conference room Please note there is a Hill shuttle from Hearst Mining Circle at 2:40 pm
"Early Results from the South Pole Telescope"
The South Pole Telescope (SPT) is a 10-meter telescope designed to survey the millimeter-wave sky, taking advantage of the exceptional observing conditions at the Amundsen-Scott South Pole Station. The telescope and its ground-breaking 960-element bolometric camera (developed at UCB) were successfully installed at the South Pole in 2007. Since then, SPT has embarked upon a large, three-frequency survey covering more than 5% of the entire sky. The primary science goal of the survey is to constrain the evolution of dark energy through a mass-limited catalogue of hundreds of SZ clusters. However, it will also produce a rich data set for exploring the properties of individual clusters and sub-millimeter galaxies, and for probing small-scale cosmic microwave background anisotropies. I will report upon on early science prospects and results from the 2008 SPT data.

Nov. 10, Tuesday 1:10 pm
Charlie Conroy, Princeton
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"The stellar population synthesis technique"
The SPS technique is deceptively simple. Relying on stellar evolution calculations, stellar spectral libraries, and dust models, practitioners of SPS aim to convert the observed spectral energy distributions of galaxies into physical properties. Knowledge of these physical properties, which range from total stellar masses to star formation rates and metallicities, are essential for understanding the formation and evolution of galaxies. The SPS framework thus provides a fundamental link between theory and observations. Despite its importance, a systematic investigation of the uncertainties in SPS is lacking. In this talk I will describe ongoing work exploring and constraining the panoply of uncertainties in SPS, including uncertainties in stellar evolution, dust models, and initial mass functions, amonst others, and their propagation into the derived physical properties of galaxies.

Nov. 16, Monday 12:10 pm (TAC seminar)
Claude-Andre Faucher Giguere,Harvard-CfA
544 Campbell Hall
tba

Nov. 17, Tuesday 1:10 pm
Eli Rykoff, UCSB
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Nov. 18, Wednesday 12:10 pm (Wednesday Theory Lunch)
Doron Lemze, Tel Aviv
544 Campbell Hall
"Multi-wavelength Studies of Galaxy Clusters and Their Use as Cosmological Probes"
The availability of extensive optical measurements of member galaxies, strong and weak gravitational lensing measurements, and resolved X-ray images, afford detailed determination of the galaxy, gas, and dark matter spatial profiles. I will describe the results from combined analyses of high quality multi-wavelength data by implementing a new, largely model-independent approach. I will then show that the contribution of clusters to the the X-ray background can be used to set meaningful constraints on alternative non-Gaussian cosmological models.

Nov. 24, Tuesday 1:10 pm
Henk Hoekstra, Leiden
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Nov. 30, Monday 12:10 pm (Cosmology and TAC seminar)
Fabian Schmidt, Caltech
544 Campbell Hall
tba

Dec. 1, Tuesday 1:10 pm
Yu Lu, U Mass Amherst
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Dec. 8, Tuesday 1:10 pm
Will Percival, Portsmouth
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Jan. 12, Tuesday 1:10 pm
Desika Narayanan, Harvard-Smithsonian, CfA
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Jan. 26, Tuesday 1:10 pm
Scott Daniel, IEU, Korea
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Feb. 2, Tuesday 1:10 pm
Jason Prochaska, Santa Cruz
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Direct Measurement of the IGM Opacity to H I Ionizing Photons"

Feb. 9, Tuesday 1:10 pm
held
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Feb. 16, Tuesday 1:10 pm
held
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Feb. 23, Tuesday 1:10 pm
Anne Zabludoff or Dennis Zaritsky, Arizona
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Feb. 25, Thursday 4:10 pm
Anne Zabludoff or Dennis Zaritsky, Arizona
(room tba)
tba

Mar. 2, Tuesday 1:10 pm
tba,
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Mar. 9, Tuesday 1:10 pm
tba,
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Mar. 16, Tuesday 1:10 pm
tba,
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Mar. 23, Tuesday 1:10 pm
spring break

Mar. 30, Tuesday 1:10 pm
tba,
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Apr. 6, Tuesday 1:10 pm
tba,
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Apr. 13, Tuesday 1:10 pm
tba,
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Apr. 20, Tuesday 1:10 pm
tba,
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Apr. 27, Tuesday 1:10 pm
Yuval Birnboim, CfA
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

May 4, Tuesday 1:10 pm
tba,
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

May 11, Tuesday 1:10 pm
tba,
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
tba

Oct. 1, Thursday 4:00 pm (LBL RPM)
Jason Rhodes, JPL
LBL 50A-5132
"The High Altitude Lensing Observatory"
The High Altitude Lensing Observatory (HALO) is a balloon-borne telescope and camera system that will constrain the properties of the dominant components of the Universe. The current concordance model in cosmology holds that the dual phenomena of dark matter and dark energy collectively comprise over 95% of the mass/energy of the Universe, but the properties of this dark sector are poorly constrained. Weak gravitational lensing, whereby the images of background galaxies are slightly distorted by foreground dark matter, is an ideal probe of dark matter and dark energy. HALO will perform a 200-1000 square degree weak lensing survey measuring the shapes of 15-20 galaxies per square arcminute while flying at 35 km. By observing at this altitude, above more than 99% of the atmosphere, HALO will be able to achieve near space-quality data, avoiding the seeing associated with ground-based telescopes. HALO will thus perform a survey that is statistically competitive to ground-based surveys in the same time frame, but with quality and systematics control close to those of a space-based survey. HALO thus represents an important intermediate step in high-precision weak lensing measurements between surveys done with the Hubble Space Telescope and ambitious space surveys planned for late in the next decade. I will present the science justification for HALO, the baseline design, and proposed survey strategy.

Oct. 6, Tuesday 1:10 pm
Caroline Zunckel, Princeton
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"The Lyman-alpha forest as a tool to study early Universe cosmology"
With the upcoming planned experiments such as the Baryon Oscillation Spectroscopic Survey (BOSS), we stand to gain a wealth of information with which to test the current standard model of cosmology. In addition to mapping the large scale distribution of 1.5 million galaxies, BOSS will probe the underlying matter distribution via the Lyman-alpha forest, observed in the absorption spectra of of 160,000 distant quasars. With each quasar spectrum providing a 1D map of the underlying density field along the line of sight, the Lyman-alpha forest survey will provide a powerful probe of the matter distribution at high redshifts. We evaluate whether such a survey can place constraints on the initial conditions of the Universe. In the standard model of cosmology, structure formed from gravitational instability of primordial fluctuations in the density field introduced by inflation. There are various completing inflationary scenarios, with the level of non-Gaussianity emerging as a key observable with which to discriminate among them. Because the 3-point function is sensitive to non-linearities, a precise measurement of the flux bispectrum could provide the necessary tool to do so. We use second order perturbation theory in order to compute the expected flux bispectrum measured from the Lyman-alpha forest and use a fisher matrix formalism to evaluate the ability of future surveys such as BOSS to constrain primordial non-Gaussianity. We also evaluate the potential of the bispectrum from the cross correlation between the flux distribution and the quasar distribution to detect this signal.

Oct. 8, Thursday 4:00 pm (LBL RPM)
Slava Turyshev, JPL
LBL 50A-5132
"Tests of Relativistic Gravity in Space: History, Recent Progress and Future Directions"
Einstein's general theory of relativity is the standard theory of gravity, especially where the modern needs of astronomy, astrophysics, cosmology and fundamental physics are concerned. As such, this theory is used for many practical purposes involving spacecraft navigation, geodesy, time transfer and etc. Series of recent experiments have successfully tested general relativity to a remarkable precision. Various experimental techniques were used to test relativistic gravity in the solar system namely spacecraft Doppler tracking, planetary ranging, lunar laser ranging, dedicated gravity experiments in space and many ground-based efforts. We will discuss the recent progress in the tests of relativistic gravity and motivation for the new generation of high-accuracy gravitational experiments in space. We also discuss the advances in our understanding of fundamental physics that are anticipated in the near future and evaluate the discovery potential of the recently proposed solar system gravitational experiments.

Oct. 8, Thursday 4:10 pm (Astronomy Colloquium)
Chris Fassnacht, Davis
2 LeConte Hall
"Galaxy Halos and Subhalos at Moderate Redshifts"
Current simulations of galaxy formation make predictions about how mass will be distributed in galaxy halos. Using the technique of gravitational lensing, it is becoming possible to measure details of mass distributions in galaxies beyond the local Universe and, thus, to compare observations directly to simulations for samples of cosmologically distant objects. I will describe results from two ongoing projects that take advantage of high- resolution space- and ground-based imaging. The first combines strong and weak gravitational lensing to quantify the relative contributions of the dark and luminous matter in galaxies on scales from 10 kpc to nearly 1 Mpc. The second focuses on detecting the CDM subhalos predicted by simulations, via both direct imaging and gravitational lens modeling.

Oct. 9 , Friday 2:00 pm (INPA journal club-time moved due to runaround)
Nico Hamaus, Zurich
LBNL 70A-3377

Large scale structure (LSS) of the universe carries a wealth of information about the physics governing cosmological evolution. Galaxies are the observable components that allow us to investigate the nature of the universe in ever greater detail using redshift surveys. However, dark matter accounts for the dominant contribution to LSS while galaxies are only biased, stochastic tracers of this underlying density field. On large scales, this bias yields a constant enhancement in clustering amplitude and can be removed to reconstruct the dark matter power spectrum. A degree of randomness (stochasticity) in the distribution of galaxies and their dark matter halos implies a limitation on the accuracy of this reconstruction. It is thus desirable to develop estimators that are least affected by this randomness in order to provide constraints on basic cosmological parameters competitive with those from other measurements, such as the cosmic microwave background (CMB) and supernovae (SN). This, in turn, can shed more light on the cause of the universe's late time acceleration and help in the distinction between dark energy and modified gravity theories.

I present a technique to optimize the information content encoded in the statistics of biased tracers of the dark matter density field, applied on numerical N-body simulations. An optimal weighting scheme that minimizes the stochasticity between halos and dark matter is presented and applied to halo catalogs to show that the signal-to-noise ratio can be enhanced considerably. The issues of mass-uncertainty and redshift-space distortions are discussed.

Oct. 12, Monday 12:10 pm (TAC seminar)
Dusan Keres, Harvard
544 Campbell Hall
"Cold Mode of Gas Accretion"
Most galaxies are actively star forming at all epochs. However, observations of cold gas reservoirs indicate that, at any epoch, there is not enough gas in dense galactic component to support evolution of star formation activity over time. This suggests that galactic gas is being replenished from the intergalactic medium. I use fully cosmological simulations of galaxy formation to study the gas supply into galactic component from high redshift to present. At high redshift "smooth" infall of cold filamentary gas dominates the gas supply of all galaxies. This "cold mode accretion" is a major driver of very active star formation of high-z galaxies enabling such activity to proceed for a significant fraction of the Hubble time. Gas accretion rates at a given halo and galaxy mass decrease with time, causing the drop in star formation rates. Properties and geometry of infalling gas change with halo mass and redshift. At low redshift some of the halos are able to cool hot virialized gas but filaments are still indirectly supplying galaxies with gas via cold gaseous clouds that form from infaling cold/warm filamentary gas. In this talk I will describe properties, physics and consequences of gas accretion, and feedback processes needed to modulate growth of galaxies over time. Finally, I will point out promising directions for future research in this area and discuss several observational probes of cold halo gas that can provide strong constraints on the physics of gas accretion in galaxies.

Oct. 13, Tuesday 1:10 pm
Donghui Jeong, Texas
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Cosmology with high (z>1) redshift galaxy surveys"
Galaxy redshift surveys are powerful probes of cosmology. Yet, in order to fully exploit the information contained in galaxy surveys, such as the distance scales, the primordial power spectrum, and neutrino masses, we need to improve upon our understanding of the structure formation in the Universe. As galaxies are formed/observed in the late time when the density field is no longer linear, understanding non-linearities, which alter the galaxy power spectrum different from the linear theory prediction, is essential. In this talk, we show that, at high redshifts, we can accurately model the galaxy power spectrum by using the standard cosmological perturbation theory. Once we model the full shape of the galaxy power spectrum in redshift space, we can extract much more cosmological information than simply using small features such as the Baryon Acoustic Oscillations. Going beyond the power spectrum, we can use the three-point function, or the bispectrum, to gain important information on the early universe as well as on the galaxy formation via measurements of primordial non-Gaussianity and galaxy bias. We show that the galaxy bispectrum is more sensitive to primordial non-Gaussianities than previously recognized, making high-redshift galaxy surveys a particularly potent probe of the physics of inflation.

Oct. 14, Wednesday 12:10 pm (Theory Lunch)
Elena D'Onghia, Harvard-CfA
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Resonant Stripping as the origin of dwarf spheroidal galaxies"
The most dark matter dominated galaxies known are the dwarf spheroidals, but their origin is still uncertain. The recent discovery of ultra-faint dwarf spheroidals around the Milky Way further challenges our understanding of how low-luminosity galaxies originate and evolve because of their even more extreme paucity of gas and stars relative to their dark matter content. By employing numerical simulations we propose that interactions between dwarf disc galaxies can excite a gravitational resonance that immediately drives their evolution into spheroidals. This effect, which is purely gravitational in nature, is distinct from other mechanisms which have been proposed up to now to explain the origin of dwarf spheroidals, such as merging, galaxy-galaxy harassment and more general heating processes, or tidal and ram pressure stripping. Using a new analytic formalism that we called "Tidal Near-Resonance Theory," I will show the efficiency and nature of this process and its applicability to a huge number of problems: from the formation of star tails in galaxies, to the formation of dwarf spheroidal galaxies, to planetary systems.

Oct. 16, Friday 12:10 pm (Astro Journal Club)
Assaf Horesh, Tel Aviv
544 Campbell Hall
"New Results for Giant Arc Statistics in ~100 Clusters Observed with HST"
Gravitational lensing is frequently used to map the evolution of cluster mass profiles, ellipticities, and substructure. One approach is to perform detailed modeling of individual clusters using strong and weak lensing, but this is generally suited only to deep data for individual clusters that exhibit numerous lensed images, and the results may not be representative of the majority of clusters. A complementary approach is to measure the statistics of lensed arcs in large samples of clusters. Over the past decade, a debate has gone on about the nature of cluster samples selected by different methods, and about whether or not real clusters are highly more efficient producers of arcs than expected from theory. I will present an analysis of the arc statistics in a sample of ~100 galaxy clusters observed with the HST/ACS. X-ray selected clusters are much more efficient lenses than optically-selected clusters of similar optical luminosity, showing that optical selection yields lower-mass, perhaps marginally bound, structures. I will also present our past and in-progress comparison of observed arc statistics with simulations that aim to include all the theoretical and observational aspects of the problem.

Oct. 20, Tuesday 1:10 pm
Mariska Kriek, Princeton
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"A Deep View on the Early Universe: Extreme Makeovers & Overweight Galaxies"
Recent studies have demonstrated that the galaxy population at z=2-3 shares characteristics with today's galaxies: massive galaxies are predominantly red, a color-density relation was already in place, and massive, quiescent galaxies form a red sequence in color-mass space. However, the high-redshift universe far from resembles the local universe. Massive galaxies at z~2.5 do not seem to represent a Hubble sequence as their structures and morphologies are different from their local analogs. Furthermore, the space density of massive galaxies still has to grow significantly, implying that many local early-type galaxies assemble or form at later times. In my talk I will discuss these similarities and differences, and their implications for our understanding of the physical processes that govern galaxy formation and evolution.

Oct. 21, Wednesday 2:00 pm (special seminar)
Tobias Marriage, Princeton
325 LeConte (Lecture room, not small room)
"The Atacama Cosmology Telescope: An Overview and Progress Report"
Over the coming decade, measurements of arc-minute scale temperature and polarization fluctuations will not only be an important tool for studying physical conditions in the early universe, but also a powerful probe of the growth of structure and of the physics of the intergalactic medium. The Atacama Cosmology Telescope (ACT) is conducting an arc-minute survey of >1000 square-degrees of sky at 148, 218, and 277 GHz. In the first part of this talk I give an overview of the ACT science goals, facility, and survey. In the second part of the talk I will detail our progress towards reducing the 148 GHz data from time-ordered-data to a power spectrum and SZ cluster catalog.

Oct. 22, Thursday 4:00 pm (LBL RPM)
Rob Crain, Swinburne
LBL 50A-5132
"GIMIC: the Galaxies-Intergalactic Medium Interaction Calculation"
I shall discuss a new series of hydrodynamical simulations that follow the formation of galaxies, from high-redshift until the present epoch, in the LambdaCDM cosmogony. A novel feature is that they simulate spherical volumes, ~20 Mpc/h in radius and with differing overdensities, extracted from the Millennium Simulation. They hence trace the evolution of all structures expected within the volumes probed by low-redshift galaxy surveys, whilst retaining sufficient detail to probe dwarf galaxies and resolve the formation of proto-galaxies at high-redshift. The simulations include treatments of gas cooling, photoheating from an ionising background, star formation, supernova feedback and chemodynamics. I shall present the initial results, focussing on environmental variation in the volume-averaged star formation rate and the formation of compact massive galaxies. I shall also discuss how hydrodynamical simulations are a useful tool for identifying weaknesses in analytic descriptions of galaxy formation, in particular demonstrating how GIMIC provides a simple resolution to the `X-ray halo problem', which has been cited as a challenge to the standard picture of galaxy formation.

Oct. 23 , Friday 12:00 noon (INPA journal club)
Mark Krumholz, Santa Cruz
LBNL 50-5026 (INPA Common Room)
"The Formation of Massive Stars"
Massive stars, those larger than 20 times the mass of the Sun, are very rare, but their extreme luminosities make them both the only type of young star we can observe in distant galaxies and the dominant energy sources in the universe today. How such stars form, however, is a longstanding mystery. Efficient radiative cooling in the dense clouds where massive stars form should favor fragmentation into objects of solar mass or smaller. Even if a collapsing cloud exceeds this mass, massive stars produce so much light that the radiation pressure they exert on the gas and dust around them is stronger than their gravitational attraction, a condition that has long been expected to prevent them from growing by accretion. Unraveling these mysteries requires new techniques for simulating gravito-radiation-hydrodynamics in three-dimensions over large dynamic ranges. I introduce these methods, and I present results from recent simulations that point toward solutions to these problems.

Oct. 23, Friday 3:00 pm (SSL Colloquium)
Judd Bowman, Caltech
SSL addition conference room
"The Dawn of 21 cm Cosmology"
The Experiment to Detect the Global EoR Signature (EDGES) is a single dipole antenna operating at the Murchison Radio-astronomy Observatory. EDGES has recently yielded the strongest direct constraints to date on 21 cm emission from the Epoch of Reionization (EoR) and should soon rule out rapid reionization scenarios. I will report on the latest EDGES measurements and forecast the unique contribution of EDGES to 21 cm cosmology in the MWA and SKA eras.

Oct. 26, Monday 12:10 pm (TAC seminar)
Volker Bromm, Austin
544 Campbell Hall
"The First Stars and Galaxies"
How and when did the cosmic dark ages end? I present simulations of the formation of the first stars and galaxies, discuss their feedback on the intergalactic medium, and describe ways to probe their signature with missions such as WMAP and the James Webb Space Telescope. The properties of the first stars are determined by the interplay between cold dark matter and the atomic and molecular physics of hydrogen. I will identify the key processes and outline the major remaining uncertainties.

Oct. 26, Monday 3:40 pm (Cadie pre-empted)
Neal Dalal, CITA
402 Le Conte (Seminar room)
"Dark Matter Halos"
In this blackboard talk I'll try to give a simple way to understand the origin of various properties of dark matter halos. First I'll discuss halo density profiles, and then time permitting, move on to halo abundance and clustering.

Oct. 27, Tuesday 1:10 pm
Daniel Grin, Caltech
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Cosmological recombination: the effect of high-n states"
Thanks to the ongoing Planck mission, a new window will be opened on the properties of the primordial density field, the cosmological parameters, and the physics of reionization. Much of Planck's new leverage on these quantities will come from temperature measurements at small angular scales and from polarization measurements. These both depend on the details of cosmological hydrogen recombination; use of the CMB as a probe of energies greater than 10¹⁶ GeV compels us to get the ~eV scale atomic physics right.
One question that remains is how high in hydrogen principle quantum number we have to go to make sufficiently accurate predictions for Planck. Using sparse matrix methods to beat computational difficulties, I have modeled the influence of very high (up to and including n=200) excitation states of atomic hydrogen on the recombination history of the primordial plasma, resolving all angular momentum sub-states separately and including, for the first time, the effect of hydrogen quadrupole transitions. I will review the basic physics, explain the resulting plasma properties, discuss recombination histories, and close by discussing the effects on CMB observables.

Oct. 29 , Thursday 4:00 pm (Astronomy Colloquium)
Paul Ho, CfA/ASIAA
2 LeConte Hall
"Preparing for ALMA First Science"
The Submillimeter Array has been in operations on Mauna Kea since 2004. Many interesting and important results have been obtained in that time, including planetary studies, dusty circumstellar disks, extremely collimated molecular outflows, circumnuclear disks in nearby galaxies, magnetic fields via dust polarization studies, and dark submillimeter galaxies at high red shifts. These studies are paving the way for the first science projects to be attempted on ALMA, currently under construction in the Atacama Desert. I will show some of our latest results.

Oct. 30 , Friday POSTPONED 12:00 noon (INPA journal club)
Lincoln Greenhill, CfA
LBNL 50-5026
"Outback Radio Cosmology: the Epoch of Reionization and the Murchison Wide-field Array"
Data that constrain theoretical pictures of how the universe was reinonized during the roughly first billion years after the Big Bang are sparse. This is the era when the building blocks of our cosmos formed, i.e., the first stars and galaxies. As a result, there is a troubling gap in the cosmological record. The Murchison Wide-field Array (MWA) is an 8000-element radio interferometer being built in Western Australia, intended to make first detections of the evolving angular power spectrum of neutral Hydrogen in the intergalactic medium during reionization. The project is shaking down a 5% demonstrator and testbed prior to build out. I will discuss basic design principles, including the novel use of High Performance Computing based on GPUs, report on the status of the project, and describe a proposed progression of pathfinders leading to a low-frequency square kilometer array somewhat after 2020.

Sep. 1, Tuesday 1:10 pm
Frank van den Bosch, Utah
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Explorations with Galaxy Group Catalogues''
The advent of large galaxy redshift surveys, such as the SDSS, allows the construction of reliable galaxy group catalogues. These are ideally suited to investigate the connection between galaxies and their environments. As an example of the various avenues of scientific exploration enabled with such group catalogues, I present various results obtained from a new galaxy group finder applied to the SDSS. In particular, I will present (i) new constraints on the efficiency and importance of star formation quenching and tidal disruption of satellite galaxies, (ii) direct evidence for halo assembly bias, and (iii) measurements of galaxy alignments on the scale of dark matter halos. In each case, I discuss the implications for our understanding of galaxy formation and evolution.

Sep. 8, Tuesday 1:10 pm
Mark Hertzberg, MIT
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Approaches to Understanding Inflation: Theory, Experiment, and Observation"
Although the observational evidence for cosmological inflation is growing, the physical mechanism behind it is still unknown. In part this is because inflation probably occurred at energy scales many orders of magnitude higher than that at man-made or astrophysical particle accelerators. So how can we learn about inflation? How does it constrain microphysical theory? One approach to answering these questions is primarily theoretical: embedding inflation in fundamental theories of quantum gravity, such as string theory. Another approach is primarily experimental: finding correlations between cosmological parameters and experimental observables, such as the Higgs boson at colliders. And another approach is primarily observational: looking for signatures left by light fields that existed during inflation, such as isocurvature fluctuations from the QCD-axion. In this talk I discuss work on all three of these approaches.

Sep. 9, Wednesday 12:10 pm
Matt McQuinn, UCB
501 Campbell Hall
"Intergalactic ^3He+ hyperfine absorption as a probe of Big Bang nucleosynthesis and HeII reionization"
I will discuss the physics of the 8.7GHz hyperfine transition of ^3He+. I will show that z>3 intergalactic 8.7 GHz absorption against radio-loud quasars can be used by present and planned interferometers to probe Big Bang nucleosynthesis and HeII reionization. The physics of how this transition is pumped is very rich and similar to that of the 21cm transition of hydrogen. I will contrast this observable with high-redshift intergalactic 21cm emission. (reference: arxiv.org:0905.1715)

Sep. 14, Monday 12:10 pm (TAC seminar)
Mike Kuhlen, UCB
544 Campbell Hall
"The Quest for the Nature of Dark Matter"
Despite having observational evidence of its existence for more than seventy years now, we still don't know the nature of Dark Matter. Recent progress in astronomical observations, laboratory experiments, theory, and numerical simulations has led to an explosion in research on this topic. Here I review some of the recent developments, with an emphasis on how ultra-high resolution cosmological numerical simulations can contribute to the quest to unravel the mystery of Dark Matter.

Sep. 15, Tuesday 1:10 pm
Jaiyul Yoo, Harvard-Cfa
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
" A New Perspective on Galaxy Clustering as a Cosmological Probe: General Relativistic Effects"
We present a general relativistic description of galaxy clustering in a FLRW universe. The observed redshift and position of galaxies are affected by the matter fluctuations and the gravity waves between the source galaxies and the observer, and the volume element constructed by using the observables differs from the physical volume occupied by the observed galaxies. Therefore, the observed galaxy fluctuation field contains additional contributions arising from the distortion in observable quantities and these include tensor contributions as well as numerous scalar contributions. We generalize the linear bias approximation to relate the observed galaxy fluctuation field to the underlying matter distribution in a gauge-invariant way. Our full formalism is essential for the consistency of theoretical predictions. As our first application, we compute the angular auto correlation of large-scale structure and its cross correlation with CMB temperature anisotropies. We comment on the possibility of detecting primordial gravity waves using galaxy clustering and discuss further applications of our formalism.

Sep. 17, Thursday 2:00 pm (Special seminar)
Chris North, Cardiff
325 LeConte Hall
CLOVER and Planck
His talk will cover a range of topics that should be of interest to those working on B-mode CMB research at Berkeley. In particular, Chris worked on the polarized foreground modeling, the field selection and the scan strategy design for CLOVER.

Sep. 22, Tuesday 1:10 pm
Dan Coe, Caltech/JPL
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Cosmological Constraints from Gravitational Lens Time Delays"
Future large ensembles of time delay lenses have the potential to provide interesting cosmological constraints complementary to those of other methods. Current constraints from 10-16 time delay lenses already yield the Hubble constant (h) in agreement with and to roughly the same level of precision (10%) as the HST Key Project which analyzed 40 Cepheids. Future surveys (Pan-STARRS, LSST, JDEM / IDECS, SKA, OMEGA) will yield hundreds or even thousands of lenses with well-measured time delays. We find in a flat universe with constant w including a Planck prior, LSST time delay measurements for ~4,000 lenses should constrain h to 0.007 (~1%), Omega_de to ~0.005, and w to ~0.026 (all 1-sigma precisions). Similar constraints could be obtained by a dedicated gravitational lens observatory (OMEGA) which would obtain precise time delay and mass model measurements for ~100 lenses with spectroscopic redshifts. Constraints for a general cosmology are presented as well. We compare these to the "optimistic Stage IV" constraints expected from weak lensing, supernovae, baryon acoustic oscillations, and cluster counts, as calculated by the Dark Energy Task Force. As with any method, there are systematics we must learn to control, and we discuss these issues.

Sep. 23, Wednesday 12:10 pm (Theory Lunch)
Doug Finkbeiner, Harvard
541 Campbell Hall
"Fermi gamma rays, the WMAP haze, and dark matter"
The Fermi Gamma-ray Space Telescope has opened a new window on the ~ 10-100 GeV sky. Observations at these energies have confirmed the synchrotron explanation for previous observations of a microwave excess in the inner Galaxy (the "WMAP haze"). The same high energy electrons that produce microwave synchrotron there must also inverse Compton scatter starlight photons up to tens of GeV. I will show (for the first time!) our analysis of the latest Fermi data and describe the electron population required to explain it. Possible sources, such as pulsars and WIMP annihilation, will be discussed. I will also show how the CMB power spectrum constrains WIMP models that could explain this emission.

Sep. 28, Monday 3:10 pm (RAL/SF/ISM)
Josh Younger, IAS
544 Campbell
"The AGN-Starburst Connection in High-Redshift ULIRGs"
Over the past twenty years, compelling observational evidence has emerged for a close and fundamental link between the growth of supermassive black holes and stellar populations. Recent models of galaxy formation predict that periods of intense star formation should be associated with rapid black hole growth. We examine the nature of the AGN-starburst connection in high-redshift ULIRGs, with a focus on submillimeter-selected galaxies, using a combination of theory and observations. Observationally, we use high-resolution submillimeter interferometric imaging to constrain the physical scale of the starburst, and radio VLBI to search for active black holes. Theoretically, we use hydrodynamic simulations of major mergers, coupled with radiative transfer calculations to predict the relative contributions of AGN and star formation. Overall, we find that high-redshift ULIRGs are likely dominated by merger-driven starbursts, rather than an infrared-luminous AGN.

Sep. 28, Monday 4:30 pm
Joe Silk, Oxford
1 LeConte
"Dark Matters"
One of the greatest mysteries in the cosmos is that it is mostly dark. Astronomers and particle physicists today are seeking to unravel the nature of this mysterious, but pervasive dark matter which has profoundly influenced the formation of structure in the universe. I will describe the complex interplay between galaxy formation and dark matter detectability and review recent attempts to measure particle dark matter by direct and indirect means.

Sep. 29, Tuesday 1:10 pm
Ali Vanderveld, Caltech
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Testing General Relativity on Cosmological Scales with Weak Gravitational Lensing"
Weak gravitational lensing is a powerful probe of modifications of General Relativity on cosmological scales, since such modifications can affect both how matter produces gravitational potential wells and how photons move within these wells. I will discuss alternative theories of gravitation and how we may constrain such theories using weak lensing observables. I will also discuss the "parametrized-post-Friedmannian" approach for obtaining model-independent constraints, in which new parameters are introduced to characterize the departure from General Relativity on large scales.

Aug. 7 , Friday 12:00 noon (INPA journal club)
Weidong Li, UCB
LBNL 50B-4205
"The Luminosity Function, Rate, and Distance of Supernova"
The Lick Observatory Supernova Search (LOSS), conducted with a 30-in robotic telescope, is one of the most successful nearby SN search engines in the past decade. Over 15,000 galaxies have been monitored in the course of the search, yielding more than 1,000 SN discoveries. Our database of images and log files allow us to construct a complete SN sample to derive the observed luminosity functions (LFs) for the different SN types. These LFs, together with other improvements in the analysis, allow us to derive the most accurate rates for the nearby SNe to date. We find a surprising correlation between the SN rates and the host galaxy sizes. I will also discuss the two-component model for the SN Ia rates. In the second part of my talk, I will discuss a method to improve the accuracy of the distance measurements toward SNe Ia, by dividing the SN Ia sample into two subclasses according to the expansion velocity measurements from their spectra. We find that the so called "high-expansion velocity" events seem to have either a different reddening law, or a different color/luminosity correlation, from the "normal-expansion velocity" events. Implications of this method will be discussed.

Aug. 7 , Friday 12:10 noon (Astronomy journal club)
Nitya Kallivayalil, MIT
Campbell 544
"Six-dimensional mapping of the Milky Way: techniques to disassemble the Galaxy"
Tidal Streams provide a powerful probe of the potential of the Milky Way halo over large Galactocentric distances and their detailed phase-space structure gives us clues as to the nature of dark matter. Powerful theoretical techniques are now available to re-construct the underlying potential from the six-dimensional phase-space parameters that describe stellar tracers. Notably absent from the presently available data-sets are full 3-D velocities. I will describe an ongoing project to remedy this situation that focuses on tracers that will provide the most powerful discriminant of halo shape and distribution, and what we ultimately hope to learn.

Aug. 25 , Tuesday 11:10 am
Romain Teyssier, (Zurich)
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Recent advances in galaxy formation theory"
I will present some recent computer simulations of galaxy formation performed within a cosmological context and I will show some interesting new aspects in galaxy formation theory. I will focus on new physical mechanism that are emerging as important players in the galaxy formation process, such as cold streams, star forming clumps and magnetic fields.

Aug. 25 , Tuesday 1:10 pm
Eric Gawiser, Rutgers
544 Campbell Hall (also videoconferenced to LBL 50A-5131)
"Lyman Alpha Emitting Galaxies at 2 < z < 3: Progenitors of Present-day L* Galaxies"
We studied the spatial clustering of 155 Lyman Alpha Emitting (LAE) galaxies at z=3.1 and 333 LAEs at z=2.1 in the MUSYC-ECDFS field. We used cosmological structure formation theory to infer the dark matter halo masses of these populations and to identify their present-day descendants. The LAEs exhibit a moderate clustering bias of b~=1.7, which implies median dark matter halo masses of 10^11 M_sun. The evolution of galaxy bias with redshift predicts that 2< z < 3 LAEs evolve into typical present-day galaxies with L~=L*. Other z>3 galaxy populations, including Lyman Break Galaxies and Active Galactic Nuclei, typically evolve into more strongly clustered present-day galaxies such as massive ellipticals and cluster members. Analysis of the spectral energy distribution of z=3.1 LAEs finds that the typical LAE has low stellar mass (10^9 M_sun), moderate star formation rate (2 M_sun/yr), a starburst component age of 20 Myr, and little dust (A_V<0.2).

Aug. 27 , Thursday 4:10 pm (Astronomy Colloquium)
Mike Boylan-Kolchin, MPA
2 LeConte
"Simulating the formation of structure in the Universe"
Numerical simulations of structure formation have become essential tools for studying cosmology and galaxy formation. I will describe some of the newest, highest resolution cosmological simulations and discuss how they are influencing our understanding of the formation and evolution of dark matter halos. I will also focus on the Milky Way as a testing ground for models of cosmology and galaxy formation. The wealth of available and forthcoming observational data will provide strong constraints on both luminous and dark matter in the Galaxy. I will discuss how combining this data with the latest generation of numerical simulations is advancing our knowledge of how galaxies form.

Aug. 28 , Friday 12:00 noon (INPA Journal Club)
Francesco de Bernardis, INFN
LBNL 50B-4205
"Determining the Neutrino Mass Hierarchy with Cosmology"
Cosmological data are known to be a powerful tool to constrain neutrino mass scale. Sensitivity of Cosmology to neutrino mass arise essentially from the peculiar imprint left by total neutrino mass on growth of structure in the Universe. In recent years atmospheric and solar neutrinos experiments have suggested the existence of differences between neutrino masses through observations of flavour oscillations. The effect on Cosmology of a splitting in neutrino masses is generally smaller than that due to the total mass and can be neglected in analysing current cosmological data. Nevertheless in the near future various experiments will reach a much higher accuracy in reconstructing matter power spectrum and could in principle become sensitive also to single neutrino masses. Here we show that future cosmic shear experiments, in combination with CMB constraints, can provide the statistical accuracy required to answer questions about differences in the mass of individual neutrino species. Allowing for the possibility that masses are non-degenerate we combine Fisher matrix forecasts for a weak lensing survey like Euclid with those for the forthcoming Planck experiment. Under the assumption that neutrino mass splitting is described by a normal hierarchy we find that the combination Planck and Euclid will possibly reach enough sensitivity to put a constraint on the mass of a single species. Using a Bayesian evidence calculation we find that such future experiments could provide strong evidence for either a normal or an inverted neutrino hierachy.

Jul. 29, Wednesday 12:10 pm
Shy Genel, Munich
501 Campbell Hall
"The growth of dark matter halos and implications for galaxy formation"
In the LCDM model galaxies form bottom-up. They grow by mergers with other galaxies as well as by accretion of gas from the IGM. I will describe how analysis of the cosmological dark matter-only Millennium and Millennium-II Simulations can help understanding the various growth modes. To this end, I will describe algorithms for constructing halo merger trees and the resulting halo merger rate in the simulations, as well as the significant role of non-merger, "smooth", accretion onto halos. Finally, I will show that under an assumption for the timescale of mergers, a population of rapidly accreting halos that are not undergoing major mergers is expected to exist at z~2, which may account for observed of star-forming galaxies at that redshift.

Cosmology Seminars in Previous Years

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