Colloquia & Seminars, 2012
2012
DateColloquia & Seminars
January 4, 2012
3:30 PM
Wednesday colloquium
Anatoly Klypin, NMSU
Large-scale clustering of BOSS galaxies
January 6, 2012
12:00 PM
Friday noon seminar
Adrian Pope, Argonne National Laboratory
HACCing the Universe: A New Framework for Cosmological Simulations on Massively Parallel Supercomputers
January 13, 2012
12:00 PM
Friday noon seminar
Matthew C Johnson, Perimeter Institute for Theoretical Physics
Observing Eternal Inflation
January 18, 2012
3:30 PM
Wednesday colloquium
Meg Urry, Yale University
The Interplay of Supermassive Black Hole Growth and Galaxy Evolution
January 20, 2012
12:00 PM
Friday noon seminar
Karl Joakim Rosdahl, CRAL - Observatoire de Lyon
Extended Lyman-alpha emission from cold accretion streams
January 27, 2012
12:00 PM
Friday noon seminar
Eric M Huff, UC, Berkeley
Magnification and Cosmic Shear from the Sloan Digital Sky Survey
February 3, 2012
12:00 PM
Friday noon seminar
Marcelle Soares-Santos, Fermilab
Weak Gravitational Lensing with the SDSS Coadd and implications for DES
February 15, 2012
3:30 PM
Wednesday colloquium
Daniel J H Chung, University of Wisconsin - Madison
The Fate of the False Vacuum in the Era of the LHC and Precision Cosmology
February 17, 2012
12:00 PM
Friday noon seminar
Adam A Lidz, University of Pennsylvania
Reionization and CO Intensity Mapping
February 24, 2012
12:00 PM
Friday noon seminar
Philip F Hopkins, UC Berkeley
Stars Formation, Black Holes, and Feedback in Galaxy Formation
February 29, 2012
3:30 PM
Wednesday colloquium
John A Johnson, Caltech
Hot on the Trail of Warm Planets Orbiting Cool M Dwarfs
March 2, 2012
12:00 PM
Friday noon seminar
Juan Estrada, Fermilab
Dark Matter Search with CCDs
March 9, 2012
12:00 PM
Friday noon seminar
Curt Cutler, Jet Propulsion Lab and Caltech
Cosmology with 300,000 Standard Sirens
March 16, 2012
12:00 PM
Friday noon seminar
Jesse Leaman, Space Science Institute
Supernova rate by subclass in the local universe
March 28, 2012
3:30 PM
Wednesday colloquium
William Kinney, Univ. at Buffalo, SUNY
Inflation, or What?
March 30, 2012
12:00 PM
Friday noon seminar
Matthew Colless, Australian Astronomical Observatory
Expansion, acceleration and growth rate of the universe from the 6dF and WiggleZ surveys
April 5, 2012
12:00 PM
Friday noon seminar
Albert Stebbins, Fermilab
WYSIWYG Space-Time
April 11, 2012
3:30 PM
Wednesday colloquium
Laura Cadonati, University of Massachusetts Amherst
Probing the Transient Universe with Gravitational Waves
April 13, 2012
12:00 PM
Friday noon seminar
Rosalind E Skelton, Yale University
The rise of the red sequence: Exploring hierarchical growth with models and future prospects with the 3DHST and CANDELS surveys
April 20, 2012
12:00 PM
Friday noon seminar
Will Percival, University of Portsmouth
First results from galaxy clustering in the BOSS survey
April 25, 2012
3:30 PM
Wednesday colloquium
Rachel Somerville, Rutgers University
The Other Side of Galaxy Formation: modeling gas in and around galaxies
April 27, 2012
12:00 PM
Friday noon seminar
Oliver Zahn, University of California, Berkeley
New Cosmology from the South Pole Telescope
May 4, 2012
12:00 PM
Friday noon seminar
Reina Maruyama, University of Wisconsin-Madison
DM-Ice: a Search for Dark Matter at the South Pole
May 9, 2012
3:30 PM
Wednesday colloquium
John Beacom, Ohio State University
Diffuse Supernova Neutrino Background
May 11, 2012
12:00 PM
Friday noon seminar
Laura Newburgh, Princeton University
ACTPol: A Polarized Receiver for the Atacama Cosmology Telescope
May 18, 2012
12:00 PM
Friday noon seminar
Vikram V Dwarkadas, University of Chicago
The Acceleration and Escape of Particles in Young Supernova Remnants
May 23, 2012
3:30 PM
Wednesday colloquium
Jonathan Feng, UC Irvine
Status of SUSY and SUSY Dark Matter
October 5, 2012
12:00 PM
Friday noon seminar
Pasquale Blasi, INAF/Arcetri Astrophysical Observatory
Acceleration of Galactic Cosmic Rays
October 10, 2012
3:30 PM
Wednesday colloquium
Rafael F Lang, Purdue University
The Search for Dark Matter with XENON
October 12, 2012
12:00 PM
Friday noon seminar
A. Emir Gumrukcuoglu, Kavli IPMU, University of Tokyo
Fate of cosmological solutions in massive gravity
October 17, 2012
3:30 PM
Wednesday colloquium
Cheng Chin, The University of Chicago
From cosmology to cold atoms: observation of Sakharov acoustic oscillations in quenched atomic superfluids
October 19, 2012
12:00 PM
Friday noon seminar
Alex Geringer-Sameth, Brown University
Results of dark matter searches in dwarf galaxies with Fermi
October 24, 2012
3:30 PM
Wednesday colloquium
Juan I. Collar, University of Chicago
Direct Detection of WIMP dark matter: the nitty-gritty
October 26, 2012
12:00 PM
Friday noon seminar
Vera Gluscevic, California Institute of Technology
CMB as a Probe of New Physics: The Story of Cosmic Birefringence
November 2, 2012
12:00 PM
Friday noon seminar
Caroline N Clark, Imperial College London
SPIDER, CMB Polarization And Modeling Polarized Microwave Foreground Emission
November 7, 2012
3:30 PM
Wednesday colloquium
Amol Upadhye, Argonne National Laboratory
Modified gravity from the micron to the megaparsec
November 9, 2012
12:00 PM
Friday noon seminar
Andrew Wetzel, Yale University
Galaxy evolution in groups and clusters in a hierarchical Universe
November 16, 2012
12:00 PM
Friday noon seminar
Tim R Linden, UC - Santa Cruz
Understanding High Energy Gamma-Ray Emission from the Galactic Center
November 30, 2012
12:00 PM
Friday noon seminar
Daniel Grin, Institute for Advanced Study
New light on cosmic initial conditions and dark matter
December 7, 2012
12:00 PM
Friday noon seminar
Simeon Bird, Institute for Advanced Study, Princeton
Neutral Hydrogen Absorption on a Moving Mesh

Large-scale clustering of BOSS galaxies
January 4, 2012 | 3:30 PM | BSLC 001 | Wednesday colloquium
Wednesday colloquium
Anatoly Klypin, NMSU

I'll discuss latest results on clustering of galaxies on scales from 100 kpc to 100 Mpc in the Baryonic Oscillations Spestroscopic Survey (BOSS). Results are compared with predictions of the LCDM model.

HACCing the Universe: A New Framework for Cosmological Simulations on Massively Parallel Supercomputers
January 6, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Adrian Pope, Argonne National Laboratory

Cosmological simulations are crucial to maximally and robustly leverage observational information from sky surveys for cosmological inference. Ambitious surveys in the next decade will place heavy demands on our simulation capabilities. I will describe a new framework for cosmological n-body simulations called the Hardware Accelerated Cosmology Code (HACC) that we have developed in order to run efficient simulations on cutting edge and next generation High Performance Computing systems.

Observing Eternal Inflation
January 13, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Matthew C Johnson, Perimeter Institute for Theoretical Physics

Inflation is a key component of the 'standard model' of cosmology. However, in many specific realizations of this idea, inflation is eternal and ceases only locally in 'pockets' or 'bubbles' that may become radiation- or matter-dominated. One of these could contain our observable universe. In this talk I will outline why eternal inflation is generic, how this idea can be tested through the observation of collisions between bubbles, and what it means to make predictions in an eternally inflating multiverse.

The Interplay of Supermassive Black Hole Growth and Galaxy Evolution
January 18, 2012 | 3:30 PM | BSLC 001 | Wednesday colloquium
Active Galactic Nuclei (AGN).
Wednesday colloquium
Meg Urry, Yale University

The growth of black holes over billions of years releases energy that may quench star formation ("feedback"). Tracing the cosmic history of black hole growth with multiwavelength surveys, we find that most AGN are heavily obscured and that obscuration is more common in the young Universe and in low-luminosity AGN. Most black hole growth takes place in moderate luminosity AGN rather than quasars, and feedback in these systems affects far more galaxies than do quasars. At z~12, we see evidence that AGN may help quench star formation (which is not the case at z~0). Perhaps surprisingly, most moderate luminosity AGN are hosted in disky galaxies, out to z~2, suggesting that major mergers do not trigger most black hole growth. Finally, we find an intriguing dependence of AGN activity on host galaxy morphology which is not yet fully explained.

Extended Lyman-alpha emission from cold accretion streams
January 20, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Gas accretion streams and tidal tails around redshift 3 galaxies in one of our cosmological zoom simulations.
Friday noon seminar
Karl Joakim Rosdahl, CRAL - Observatoire de Lyon

I present results from a set of cosmological simulations designed to study the observability of cold accretion streams at redshift 3 via Lyman-alpha (Lya) radiation and the feasibility of said streams as the driver of Lya blobs (or LABs). These simulations are unique because for the first time we include fully coupled radiative transfer of the UV radiation background with our newly developed RT version of the Ramses code and hence obtain a consistent model of self-shielding. This provides us with an accurate estimate of gas temperatures and neutral hydrogen fractions, which in turn allows us to accurately estimate the Lya emissivity of extended structures. I discuss the efficiency of gravitational heating in streams to power extended Lya emission and illustrate some of the complexities involved in extracting accurate observables from simulations. I show our overall resulting LAB luminosities and morphologies and compare with observations. Our main results are that the cold accretion streams in massive halos of >10^12 solar masses are capable of powering LABs and we predict that cold accretion streams should be unambiguously observable in the near future with upcoming instruments. (Based on arXiv:1112.4408v1.)

Magnification and Cosmic Shear from the Sloan Digital Sky Survey
January 27, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Eric M Huff, UC, Berkeley

Abstract: I discuss results from a cosmic shear measurement in the Sloan Digital Sky Survey. We have coadded 250 square degrees of multi-epoch SDSS imaging along the celestial equator, optimizing for weak lensing measurement. We employ standard techniques for shape measurement, shear calibration, and inference of the redshift distribution, and perform a wide array of tests that show that the systematic errors for this measurement are dominated by the statistical errors. We analyze the shear autocorrelation with and without WMAP7 priors, and produce competitive constraints on the matter density and the amplitude of the matter power spectrum.

I will also discuss some new results on lensing magnification. Motivated by the need for greater signal-to-noise in weak lensing measurements, we have used tight photometric galaxy scaling relations to measure a galaxy-galaxy magnification signal with many times the signal-to-noise of earlier magnification results. I describe how minor improvements on this work may permit magnification measurements with signal comparable to shear.

Weak Gravitational Lensing with the SDSS Coadd and implications for DES
February 3, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Marcelle Soares-Santos, Fermilab


The Fate of the False Vacuum in the Era of the LHC and Precision Cosmology
February 15, 2012 | 3:30 PM | BSLC 001 | Wednesday colloquium
Wednesday colloquium
Daniel J H Chung, University of Wisconsin - Madison

The LHC guarantees to grant us insight into the origin of electroweak symmetry breaking. When combined with precision cosmological data, this will allow for a partial reconstruction of a new rung in the historical ladder of early universe cosmology, particularly regarding how the universe transitioned from the electroweak symmetry preserving false vacuum to the true vacuum that we live in today. In addition to the electroweak phase transition, I examine what other phase transition related information we may hope to obtain in the foreseeable future. The topics discussed from this perspective will include electroweak baryogenesis, dark matter, dark energy, gravity waves, and the implications of the recent hint of the Higgs boson at 125 GeV.

Reionization and CO Intensity Mapping
February 17, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Adam A Lidz, University of Pennsylvania

One of the primary goals of observational cosmology at present is to detect, and elucidate the nature of, the Epoch of Reionization (EoR) when early galaxies and quasars turn on and photo-ionize 'bubbles' of neutral hydrogen gas in their surroundings. I will start by reviewing recent observational progress in understanding reionization: while these observations provide intriguing hints, they have yet to reveal a consistent story, and the detailed nature of the EoR remains mysterious. The most promising way to improve our understanding of the EoR is to detect redshifted 21 cm emission from the intergalactic medium during reionization. I will describe how measurements of large scale structure in the galaxy distribution during the EoR, while challenging, would provide an important complement to future redshifted 21 cm observations. I will discuss how it might be possible to study large scale structure during reionization using rotational emission lines from CO molecules in high redshift star-forming galaxies.

Stars Formation, Black Holes, and Feedback in Galaxy Formation
February 24, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Philip F Hopkins, UC Berkeley

Many of the most fundamental unsolved questions in star and galaxy formation revolve around star formation and "feedback" from both massive stars and accretion onto super-massive black holes. The combination of models with realistic gas and feedback physics have led to huge shifts in our understanding of when and how galaxies grow, where stars form within them, and what their ultimate fate will be. I'll review the current status of our understanding of these feedback processes, and present new models which attempt to realistically model the diverse physics of the interstellar medium, star formation, and feedback from stellar radiation pressure, supernovae, and photo-ionization, and their interplay with feedback from luminous quasars. These mechanisms lead to 'self-regulated' galaxy and star formation, in which global correlations such as the Schmidt-Kennicutt law, the black hole-host galaxy correlations, and the global inefficiency of star formation emerge naturally. I'll discuss how, within galaxies, feedback regulates the structure of the interstellar medium, the collapse of dense gas into star-forming cores, and black hole accretion rates. But feedback also produces galactic super-winds that can dramatically alter the cosmological evolution of galaxies, their behavior in galaxy mergers, and structure of the inter-galactic medium. I'll highlight how a combination of improved theoretical models and observations can elucidate the physics driving these winds and their role in phenomena on an enormous range of spatial scales.

Hot on the Trail of Warm Planets Orbiting Cool M Dwarfs
February 29, 2012 | 3:30 PM | BSLC 001 | Wednesday colloquium
Wednesday colloquium
John A Johnson, Caltech

Just three years ago the prospect of finding temperate, rocky worlds around other stars was still the subject of science fiction: none had been found and reasonable estimates put us years or decades away from such a momentous discovery. All of that has changed very recently on the heels of the extraordinarily successful NASA Kepler mission. By searching for the tiny diminutions of starlight indicative of an eclipsing planet, Kepler has produced thousands of new planet candidates orbiting distant stars. Careful statistical analyses have shown that the majority of these candidates are bona fide planets, and the number of planets increases sharply toward Earth-sized bodies. Even more remarkably, many of these planets are orbiting right "next door," around tiny red dwarf stars, several of them residing the the Goldilock's zone where temperatures are amenable to the existence of liquid water. I will describe our multi-telescope campaign to validate and characterize these micro planetary systems, and present some early, exciting results that point the way to the first detection of the first Earth-sized planet in the habitable zone of a star.

Dark Matter Search with CCDs
March 2, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Juan Estrada, Fermilab

Current status of the low threshold dark matter search with CCDs in the DAMIC experiment.

Cosmology with 300,000 Standard Sirens
March 9, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Curt Cutler, Jet Propulsion Lab and Caltech

I will describe work showing that a highly sensitive deci-Hz gravitational-wave mission, like BBO or Decigo, could measure cosmological parameters, such as the Hubble constant H_0 and the dark energy parameters w_0 and w_a, more accurately than other proposed dark-energy missions, and with less problematic systematics. The basic point is that BBO's angular resolution is so good that it will provide us with hundreds of thousands of "standard sirens." These standard sirens are inspiraling neutron star and black hole binaries, with gravitationally-determined distances and optically determinable redshifts. I also explain why BBO would also be a powerful weak lensing mission, and I mention some possibilities for de-scoping the mission.

Supernova rate by subclass in the local universe
March 16, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Jesse Leaman, Space Science Institute


Inflation, or What?
March 28, 2012 | 3:30 PM | BSLC 109 | Wednesday colloquium
Wednesday colloquium
William Kinney, Univ. at Buffalo, SUNY

Inflation has emerged as the leading model for the very early universe, not least because of the theory's remarkably successful prediction for the form of the CMB anisotropy. I ask the question: is inflation the only way to match the data? If not, what do the possible alternatives look like?

Expansion, acceleration and growth rate of the universe from the 6dF and WiggleZ surveys
March 30, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Matthew Colless, Australian Astronomical Observatory

The 6dF Galaxy Survey has mapped 125,000 galaxies at a median redshift z=0.05 over the whole southern hemisphere, while the WiggleZ survey has mapped 220,000 star-forming galaxies at redshifts out to z=1 over a cubic gigaparsec. In combination, these surveys measure the evolution of the power spectrum of the galaxy distribution, including the features due to the baryon acoustic oscillations and redshift-space distortions. These measurements yield the expansion history of the universe over the last 8 billion years, and provide new and model-independent determinations of the Hubble constant at low redshift, the rate of acceleration since z=1, and the growth of large-scale structure. They also give an improved upper limit on the sum of the neutrino masses.

WYSIWYG Space-Time
April 5, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Albert Stebbins, Fermilab

An observationally based, non-perturbative approach to learning about the space-time geometry of our universe.

On macroscopic scales new forces are determined by measuring accelerations e.g. Newton and Kepler for gravity, or balancing known with unknown forces in a static configuration. Dark energy is a putative gravitationally repulsive substance which permeates our universe, yet the evidence for it involves neither technique, but is rather a mix of observations and assumptions about the geometry of space-time and initial conditions. In fact much of cosmology is done this way. Here I examine what one can learn about space-time geometry purely by observations from a single vantage point of distant objects and their motions and, in particular, not assuming the cosmological principle. A formalism is developed whereby all of space-time geometry is expressed in terms of observables. Some new and interesting formulae are derived and a possible future path for dark energy studies is given.

Probing the Transient Universe with Gravitational Waves
April 11, 2012 | 3:30 PM | BSLC 109 | Wednesday colloquium
Wednesday colloquium
Laura Cadonati, University of Massachusetts Amherst

The Laser Interferometer Gravitational-wave Observatory (LIGO) and its sister project Virgo aim to achieve, within this decade, the first direct detection of gravitational waves and tune in to the gravitational-wave soundtrack of the Universe. The information from gravitational waves, complementary to the multi-wavelength electromagnetic spectrum, neutrinos and cosmic rays, will contribute to a more complete, understanding of some of the most violent and energetic events in the universe, such as gamma-ray bursts, soft-gamma repeaters, supernovae, and glitching pulsars.
In this talk I will give an overview of ongoing efforts towards the realization of this new gravitational wave astrophysics, and of how electromagnetic and neutrino observations and the theoretical understanding of source dynamics are coupled into gravitational wave analysis. I will present selected results from the initial generation of LIGO and Virgo data and outline prospects for discovery in the advanced detector era, with particular focus on transient signatures.

The rise of the red sequence: Exploring hierarchical growth with models and future prospects with the 3DHST and CANDELS surveys
April 13, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
A major merger observed with the 3D-HST survey.
Friday noon seminar
Rosalind E Skelton, Yale University

The massive quiescent galaxies we see at low redshifts seem to evolve slowly and passively, having formed at high redshift. The role of mergers in their formation and growth is strongly debated, as there does not seem to be much room for growth based on the observed luminosity evolution. I will describe the simple models we have used to test how hierarchical growth affects red sequence galaxies from z=1 to z=0. We find that the changes in color and luminosity for a population that builds up through mergers are very similar to those of an old, passively evolving population, but imply very different mass growth. The observed evolution can be equally well explained as the result of hierarchical growth. I will discuss how the large new surveys 3DHST and CANDELS will extend our understanding of the role of mergers and the build up of bulges to lower masses and out to higher redshifts.

First results from galaxy clustering in the BOSS survey
April 20, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Will Percival, University of Portsmouth

First results are presented from galaxy clustering measurements in the Baryon Oscillation Spectroscopic Survey (BOSS), which is part of SDSS-III. Data release 9, due for public release in July, contains 327,349 massive galaxies with an effective redshift z=0.57 covering 3,275 square degrees. Assuming a concordance LCDM cosmological model, this is equivalent to 0.77 h^{-3} Gpc^3, and represents the largest sample of the Universe ever surveyed at this density. I will present results including Baryon Acoustic Oscillation (BAO), Redshift-Space Distribution (RSD) measurements, and cosmological constraints from full fits to the clustering signal. In particular, including the BAO measurements alongside previous measurements, results in a BAO distance ladder, which will be compared to current supernovae measurements.

The Other Side of Galaxy Formation: modeling gas in and around galaxies
April 25, 2012 | 3:30 PM | BSLC 109 | Wednesday colloquium
Wednesday colloquium
Rachel Somerville, Rutgers University

Much observational work has focused on measuring the star formation rate in galaxies and its cosmic evolution. However, the supply rate of fuel for star formation (cold dense gas), the internal processes that regulate its conversion into stars, and the feedback processes that regulate star formation, all remain poorly understood both theoretically and observationally. I will discuss recent attempts to build more sophisticated theoretical models to predict the multi-phase gas content of galaxies, which in particular will allow us to make connections between galaxies as observed via stellar emission, emission in CO or HI, and in absorption.

New Cosmology from the South Pole Telescope
April 27, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Oliver Zahn, University of California, Berkeley

I will talk about two ongoing cosmological revolutions that are fueled by high angular resolution and high sensitivity observations of the Cosmic Microwave Background: constraining the properties of the first sources of radiation in the universe via the kinetic Sunyaev-Zel'dovich effect, and constraining astroparticle and gravitational physics via lensing of the CMB. I will report on the status and prospects of these endeavors.

DM-Ice: a Search for Dark Matter at the South Pole
May 4, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Reina Maruyama, University of Wisconsin-Madison

I will describe DM-Ice, a proposed dark matter experiment at the South Pole. The aim of the experiment is to test the claim for an observation of dark matter by the DAMA collaboration by carrying out an experiment with the same detector technology, but in the southern hemisphere. By going to the opposite hemisphere, many of the suspected backgrounds would produce annual modulation with the opposite phase whereas the dark matter signature should stay the same. A 17-kg detector was installed in the Antarctic ice at the South Pole in December 2010 and is currently taking data. The full-scale experiment that can test DAMA's claim is currently being designed. I will report on the status of DMIce-17 and the plans for the full-scale experiment.

Diffuse Supernova Neutrino Background
May 9, 2012 | 3:30 PM | BSLC 109 | Wednesday colloquium
The Super-Kamiokande detector, shown here, is roughly 40 m in all directions. At any instant, it contains 10-100 neutrinos that were born in core-collapse supernovae across the cosmos. Can you spot them? Look for the red-and-white-striped sweaters.
Wednesday colloquium
John Beacom, Ohio State University

The diffuse supernova neutrino background (DSNB) is the weak glow of MeV neutrinos and antineutrinos from distant core-collapse supernovae. The DSNB has not been detected yet, but the Super-Kamiokande upper limit on the electron antineutrino flux is close to predictions, now quite precise, based on astrophysical data. If SK is modified with dissolved gadolinium to reduce detector backgrounds, then it should detect the DSNB at a rate of a few events per year, providing a new probe of supernova neutrino emission and the cosmic core-collapse rate. Neutrino astronomy, while uniquely powerful, has proven extremely difficult - only the Sun and the nearby Supernova 1987A have been detected to date - so the promise of detecting new sources soon is exciting indeed.

ACTPol: A Polarized Receiver for the Atacama Cosmology Telescope
May 11, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Laura Newburgh, Princeton University

ACTPol is a ground-based experiment designed to measure the polarization of the Cosmic Microwave Background at arcminute scales. The ACTPol receiver will feature three independent arrays each with ~1000 polarization-sensitive feedhorn-coupled TES bolometers, giving a factor of ~4 improvement in sensitivity compared to the existing receiver for the 6m Atacama Cosmology Telescope (ACT). Our observation strategy will include survey regions chosen to overlap with other multi-frequency surveys. The resulting combination of sensitive maps enables a wide range of measurements and cosmological constraints including the spectrum from gravitational lensing, the sum of the neutrino masses, the number of relativistic species, the spectral shape of the primordial power spectrum, and the primordial helium abundance, along with many more. I will present an instrument overview, science goals, and the status of the first array, set to deploy this year.

The Acceleration and Escape of Particles in Young Supernova Remnants
May 18, 2012 | 12:00 PM | KPTC 206 (Note Location) | Friday noon seminar
Friday noon seminar
Vikram V Dwarkadas, University of Chicago

The acceleration of high-energy particles to relativistic energies is a long-standing problem that has been highlighted in recent times, with the growth of various gamma-ray and cosmic ray facilities, and the Fermi space telescope. Of particular importance are the properties of the accelerator and their relation to the spectrum of accelerated particles, and the energies to which particles are accelerated.

Combining numerical simulations of supernova remnant (SNR) evolution with a solution of the cosmic-ray transport equation in test-particle mode, we study the acceleration of particles at forward and reverse shocks in both Type Ia and core-collapse SNRs. We include the effect of various magnetic field profiles in the shocked interaction region. We study the temporal evolution of the non-thermal particle distribution, and synthesize surface brightness maps for various radiation mechanisms. We investigate how the spectrum of escaped particles depends on the time-dependent acceleration history in young SNRs, and calculate the time-dependent gamma-ray spectra from molecular clouds illuminated by the escaping cosmic-rays. We also study the maximum energy of the escaped particles, and its evolution with time, and provide analytic approximations for the same.

Status of SUSY and SUSY Dark Matter
May 23, 2012 | 3:30 PM | BSLC 109 | Wednesday colloquium
Wednesday colloquium
Jonathan Feng, UC Irvine

Weak-scale supersymmetry has long been a dominant paradigm for physics beyond the standard model and particle dark matter, but it is now being challenged by a wealth of experimental data. I will begin by reviewing attempts to quantify naturalness in supersymmetry, stressing the many subjective choices that impact the results both quantitatively and qualitatively. I then summarize experimental results that most directly challenge weak-scale supersymmetry, including recent results from the LHC. Some models are excluded or under great tension, while others remain perfectly viable. For the latter, I will outline the key features, current status, and implications for colliders and dark matter searches.

Acceleration of Galactic Cosmic Rays
October 5, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Pasquale Blasi, INAF/Arcetri Astrophysical Observatory

I will discuss the crucial role played by two phenomena that have recently been investigated in the context of cosmic ray (CR) acceleration in Galactic sources (but not only): 1) plasma instabilities induced by the streaming of accelerated particles ahead of a shock front; 2) presence of neutral atoms in the acceleration region. Both effects play a crucial role in non-linear theories of CR acceleration at shock fronts. The former is especially crucial for creating the level of magnetic turbulence required to explain both high maximum energies and the observed X-ray rims in supernova remnants. The presence of neutrals has been shown to lead to several diagnostics of the acceleration process, such as the anomalous broadening of Balmer lines from supernova shocks. Moreover, given the collisionless nature of supernova shocks (and of most astrophysical shocks) neutrals behave very differently from ions and can be shown to lead to steeper spectra of accelerated particles, as a consequence of the shock modification due to the coupling of neutrals to ions through charge exchange reactions and ionization. I will discuss these topics in direct connection with the problem of the origin of Galactic cosmic rays.

The Search for Dark Matter with XENON
October 10, 2012 | 3:30 PM | BSLC 001 | Wednesday colloquium
Wednesday colloquium
Rafael F Lang, Purdue University

We know that most of the matter in the Universe is Dark Matter, but we don't know what Dark Matter is made of. Current and upcoming detectors have the sensitivity to detect or exclude Weakly Interacting Massive Particles (WIMPs) as candidates for Dark Matter. In this talk, I will review the basics of the direct search for WIMPs and give a quick overview of the current status of the field. The XENON100 experiment in particular is a leading experiment in this search and will be presented in some detail, together with recent results from a search in 225 live days of data. An outlook on where we are headed in the next few years will be given.

Fate of cosmological solutions in massive gravity
October 12, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Massive gravity has self-accelerating solutions, which may account for the present day acceleration without the need for a bare cosmological constant. Generically, the value of the graviton mass is of the order of Hubble rate today. But are these solutions stable?
Friday noon seminar
A. Emir Gumrukcuoglu, Kavli IPMU, University of Tokyo

The construction of a finite-range gravity theory has been one of the major challenges in classical field theory for the last 70 years. Recently, de Rham, Gabadadze and Tolley constructed a nonlinear theory of massive gravity, which successfully removes the unwanted extra degree that contaminated earlier constructions. The theory allows for homogeneous and isotropic solutions with self acceleration, providing an alternative to dark energy. However, the perturbation analysis shows that at linear level, these solutions contain only 2 propagating degrees of freedom, as opposed to 5 expected from a massive spin-2 particle. I will show that at nonlinear order, the additional 3 degrees acquire non-vanishing kinetic terms. For one of these degrees, the sign of the kinetic term is always negative, leading to a ghost instability in the homogeneous and isotropic background. I will conclude by presenting a new anisotropic solution which looks isotropic at the background level. For this solution, the nonlinear ghost which appears in the purely isotropic solution may be evaded.

From cosmology to cold atoms: observation of Sakharov acoustic oscillations in quenched atomic superfluids
October 17, 2012 | 3:30 PM | BSLC 001 | Wednesday colloquium
Wednesday colloquium
Cheng Chin, The University of Chicago

Sakharov oscillation, conventionally discussed in the context of early universe evolution and the anisotropy of cosmic microwave background radiation, is the manifestation of interfering acoustic waves generated in an ideal fluid. We report a laboratory observation of Sakharov oscillations in a quenched atomic superfluid. We quench the interactions between atoms and monitor the subsequent density fluctuations at different time and length scales. Sakharov oscillations are identified as the multi-peak structure in the density power spectrum, resembling that of the cosmic microwave background radiation.
From the oscillations, we determine the sonic horizon, providing new perspectives to extend quantum simulation to other intriguing cosmological and gravitational phenomena

Results of dark matter searches in dwarf galaxies with Fermi
October 19, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Image credit: NASA/DOE/Fermi-LAT Collaboration/Koushiappas and Geringer-Sameth/Brown University
Friday noon seminar
Alex Geringer-Sameth, Brown University

I will present new results from a search for both continuum and line emission from dark matter annihilation in Milky Way dwarfs. These results are based on the joint analysis of dwarf galaxy data from the Fermi Gamma-ray Space Telescope using a statistically optimal weighting of individual photons including both spatial and spectral information. This new technique, applied to the indirect dark matter search, is strong enough to probe generic WIMP candidates that reproduce the relic abundance. I will discuss the details of the framework and how it may be applied to other situations, including making predictions for future experiments.

Direct Detection of WIMP dark matter: the nitty-gritty
October 24, 2012 | 3:30 PM | BSLC 001 | Wednesday colloquium
Wednesday colloquium
Juan I. Collar, University of Chicago

I'll present an update on the status of dark matter direct detection experiments, with particular emphasis on details that the non-experimentalist may ignore, or the experimentalist may hide. I will also focus on local activities in this area (COUPP, CoGeNT, DAMIC, and dedicated calibration experiments for a number of target materials).

CMB as a Probe of New Physics: The Story of Cosmic Birefringence
October 26, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Vera Gluscevic, California Institute of Technology

Cosmological birefringence is a postulated rotation of the linear polarization of photons that arises due to a Chern-Simons coupling of a new scalar field to electromagnetism. In particular, it appears as a generic feature of simple quintessence models for Dark Energy, and therefore, should it be detected, could provide insight into the microphysics of cosmic acceleration. Prior work has sought this rotation, assuming the rotation angle to be uniform across the sky, by looking for the parity-violating TB and EB correlations in the CMB temperature/polarization. However, if the scalar field that gives rise to cosmological birefringence has spatial fluctuations, then the rotation angle may vary across the sky. In this talk, I will present the results of the first CMB-based search for direction-dependent cosmological birefringence, using WMAP-7 data, and report the first constraint on the rotation-angle power spectrum for multipoles up to the resolution of the instrument. I will discuss the implications for a specific (scale-invariant) model for rotation, and show forecasts for Planck and future experiments. I will then briefly comment on other parity-violating physical models, such as chiral gravity, and show how they can be distinguished from birefringent rotation. I will conclude by demonstrating how the same analysis can be used to probe inhomogeneous cosmic reionization, and discuss current constraints on a simple reionization model whose parameters can be figures of merit for future experiments.

SPIDER, CMB Polarization And Modeling Polarized Microwave Foreground Emission
November 2, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Caroline N Clark, Imperial College London

I will give a brief update on the SPIDER experiment, a suborbital polarimeter aimed at detecting B-mode polarization of the CMB. Given that foregrounds are expected to dominate the potential B-mode signal over all targeted observing frequencies, I will move on to present templates of the dominant Galactic foreground emissions, synchrotron and thermal dust. I will describe the inputs to this model, which includes a 3D description of the Galactic magnetic field on large and small scales as well as the dust and cosmic ray density distributions and details of alignment mechanisms. These templates may prove useful for testing foreground contamination levels in patches targeted by experiments and component separation methods and in constraining parameters in Galactic magnetic field models. I will confront the model with some available data, namely the WMAP MCMC templates of foreground emission, as an indication of the reliability of the model.

Modified gravity from the micron to the megaparsec
November 7, 2012 | 3:30 PM | BSLC 001 | Wednesday colloquium
Wednesday colloquium
Amol Upadhye, Argonne National Laboratory

The observed cosmic acceleration hints at a low-energy modification to General Relativity which could give rise to fifth forces and new particles. After describing f(R), chameleon, and symmetron models, I will discuss constraints on the resulting fifth forces from laboratory torsion pendulum experiments, the stability of stars, and the dynamics of large-scale cosmic structure. In particular, laboratory experiments are on the verge of testing interesting classes of chameleon and symmetron fifth forces. I will also show how new particles predicted by these models, which might be produced through photon interactions in stars or the laboratory, can be used to constrain modifications to gravity.

Galaxy evolution in groups and clusters in a hierarchical Universe
November 9, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Andrew Wetzel, Yale University

Satellite galaxies in groups and clusters play a critical role in the picture of galaxy evolution. As many as a third of all galaxies are satellites, and satellite star formation quenching is the dominant process in building the red-sequence population at low mass. I will present an observational and theoretical investigation into the evolution of star formation in satellite galaxies, using the Sloan Digital Sky Survey to examine satellites across a wide range of host halo masses, from massive clusters to the lowest mass dwarf galaxy groups in the local Universe. I will place these results in a fully cosmological context using a high-resolution simulation to track satellite orbits and infall times, showing that satellite star formation histories follow a delayed-then-rapid quenching scenario. I also will examine the curious evolution of satellites that orbit beyond their host halo's virial radius.

Understanding High Energy Gamma-Ray Emission from the Galactic Center
November 16, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Tim R Linden, UC - Santa Cruz

Recent data taken at TeV energies (by Atmospheric Cherenkov Telescopes) and at GeV energies (by the Fermi-LAT) have opened a new window into studies of the Galactic center. The high angular resolution of these observations make them especially well-suited to understanding the many energetic processes occurring in this dense region. Interestingly, Fermi-LAT observations have uncovered an apparent excess of ~1 GeV photons peaked around the galactic center compared to the smooth power-law observed by TeV telescopes. In this talk, I will discuss several convincing models for the peculiar emission spectrum and morphology in this region, including the annihilation of particle dark matter, a yet-undiscovered population of millisecond pulsars, and hadronic emission processes from the central black hole. Additionally I will consider the extremely interesting observation by Weniger (2012) indicating the observation of a gamma-ray line by the Fermi-LAT with an energy of 130 GeV, and will briefly discuss the instrumental, dark matter, and astrophysical phenomena which may be responsible for this observation.

New light on cosmic initial conditions and dark matter
November 30, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Daniel Grin, Institute for Advanced Study

Deviations from adiabaticity and Gaussianity in the early universe may shed light on the physics seeding primordial fluctuations. I will discuss statistical techniques to extract local-type non-Gaussianity in the presence of the full CMB transfer function. I will discuss CMB methods to probe isocurvature fluctuations between baryons and dark matter (undetectable in linear theory), as well as a new limit to this mode. Extremely light axionic dark matter (m < 10^{-18}) is in theoretical vogue, and I will discuss ongoing work to search for such axions using large scale structure and the CMB. I will close with the results of a new telescope search for decaying relic axions.

Neutral Hydrogen Absorption on a Moving Mesh
December 7, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Simeon Bird, Institute for Advanced Study, Princeton

I will present recent work performing cosmological simulations using the new moving mesh technique implemented in Arepo. Specifically, I have looked at the distribution of damped Lyman-alpha absorbers in Arepo, as compared to the SPH code Gadget. I have also compared the Lyman-alpha forest region between the two codes. Since both Arepo and Gadget use identical gravity solvers, but different methods for solving the Euler equations, we can use this comparison to assess how numerical effects associated with the hydro-solver impact observable results.