January 4, 2012 | 3:30 PM | BSLC 001 | Wednesday colloquium Large-scale clustering of BOSS galaxies 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.
January 11, 2012 | 3:30 PM | BSLC 001 | Astronomy Colloquium Why I compute.... Robert Rosner, University of Chicago
January 18, 2012 | 3:30 PM | BSLC 001 | Wednesday colloquium The Interplay of Supermassive Black Hole Growth and Galaxy Evolution Meg Urry, Yale University
Active Galactic Nuclei (AGN).
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~1ÿÿ2, 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.
January 25, 2012 | 3:30 PM | BSLC 001 | Astronomy Colloquium Looking for Dark Matter here, there and everywhere Patrick Fox, FNAL
The hunt for physics beyond the standard model at the LHC is in full swing. We already know of the existence of (at least) one new particle that is not in the standard model, dark matter. The existence of dark matter was first inferred from astrophysical observations and later confirmed by cosmological measurements. There is considerable ongoing effort to see the effects of dark matter, which makes up the majority of the matter in our galaxy, in a more terrestrial setting. I will outline what is, and what is not, known about dark matter, and explain how we may soon learn a lot more, as well as explaining how the conventional search methods can be complemented by searches at the LHC, and elsewhere.
February 1, 2012 | 3:30 PM | BSLC 001 | Astronomy Colloquium The DARKSIDE of Dark Matter Luca Grandi, Princeton University
The search for Dark Matter represents one of the most intriguing open frontiers in modern cosmology and astroparticle physics. The science case is extremely strong: observations of the cosmic microwave background fluctuation, large-scale galaxy surveys, studies of large scale structure formation and of the dynamics of galaxy clusters, all point to the existence of cold dark matter. Weakly Interacting Massive Particles (WIMPs) are an excellent candidate for cold dark matter. These particles, predicted in many new theories extending beyond the standard model, may collide with ordinary nuclei via ultra-weak interactions, and could be detected by means of special, low-background detectors, capable of selectively identifying nuclear recoils - the likely signature of WIMP interactions. I will present and discuss the DarkSide Project for direct dark matter detection. The use of depleted argon as a target in a two-phase time projection chamber, coupled with a powerful neutron veto based on the Borexino technology, results in a unique detector, capable of achieving background-free conditions. DarkSide-50 is the first detector in the DarkSide program, featuring an active mass of 50 kg of depleted argon. It is designed to reach a sensitivity to the WIMP interaction cross section of 10^-45 cm^2 and will be deployed at Laboratori Nazionali del Gran Sasso in Italy in 2012.
February 8, 2012 | 3:30 PM | BSLC 001 | Astronomy Colloquium Constraining Cosmology using the Growth of Structure and the Cosmic Microwave Background Brad Benson, University of Chicago
While dark energy explains the apparent acceleration of the universe, its properties and nature remains a complete mystery. Measurements of the growth of structure are affected by dark energy in a fundamentally different way than distance-redshift based tests, such as from type Ia supernovae and baryon acoustic oscillations. This makes them useful to break cosmological parameter degeneracies, reduce systematic uncertainty, and are an important systematic test of the standard dark energy paradigm. I will present the most recent cosmological constraints from the South Pole Telescope (SPT), and discuss the role of multi-wavelength cluster observations, primarily through Chandra X-ray and optical weak lensing observations, in improving the dark energy constraints for the full SPT cluster survey. I will also discuss the role of these observations in helping to understand the formation and evolution of massive clusters, and their relevance to future cluster surveys, such as the Dark Energy Survey. Finally, I will discuss the next frontier for CMB experiments of using the lensing of the CMB to measure the growth of structure, the technological challenges for the next generation of experiments, and their projected constraints on dark energy, neutrino mass, and the energy scale of Inflation.
February 15, 2012 | 3:30 PM | BSLC 001 | Wednesday colloquium The Fate of the False Vacuum in the Era of the LHC and Precision Cosmology 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.
February 22, 2012 | 3:30 PM | BSLC 001 | Astronomy Colloquium What Stars are Useful For - A Particle Physicist's Point of View Alex Friedland, Los Alamos National Laboratory
Stars realize a variety of physical conditions inaccessible in the lab. Various stages of stellar evolution are influenced by microphysical processes that are sensitive to the fundamental properties of elementary particles. This makes it possible to use stars to search for new particle physics beyond the Standard Model. I will show some examples of resulting bounds, including scenarios with neutrino magnetic moment, extra space-time dimensions, and axion particles. As a particularly amusing example of conditions that cannot be reproduced in the lab, I will discuss the phenomenon of collective oscillations of neutrinos streaming out of the supernova core.
February 29, 2012 | 3:30 PM | BSLC 001 | Wednesday colloquium Hot on the Trail of Warm Planets Orbiting Cool M Dwarfs 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.
March 14, 2012 | 3:30 PM | BSLC 001 | Astronomy Colloquium Observational constraints on the kinetic luminosity of quasar outflows: A key to assessing real AGN feedback mechanisms Nahum Arav, University of Colorado, Boulder
The potential importance of quasar outflows on the growth of super-massive black holes, enrichment of the intergalactic medium, evolution of the host galaxy, cluster cooling flows and the luminosity function of quasars has been widely recognized. I will briefly review these theoretical developments and describe the efforts of our research group, and others, to determine the most relevant parameter for these models: kinetic luminosity of observed quasar outflows.
January 6, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar HACCing the Universe: A New Framework for Cosmological Simulations on Massively Parallel Supercomputers 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.
January 13, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar Observing Eternal Inflation 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.
January 20, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar Extended Lyman-alpha emission from cold accretion streams Karl Joakim Rosdahl, CRAL - Observatoire de Lyon
Gas accretion streams and tidal tails around redshift 3 galaxies in one of our cosmological zoom simulations.
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.)
January 27, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar Magnification and Cosmic Shear from the Sloan Digital Sky Survey 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.
February 3, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar Weak Gravitational Lensing with the SDSS Coadd and implications for DES Marcelle Soares-Santos, Fermilab
February 17, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar Reionization and CO Intensity Mapping 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.
February 24, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar Stars Formation, Black Holes, and Feedback in Galaxy Formation 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.
March 2, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar Dark Matter Search with CCDs Juan Estrada, Fermilab
Current status of the low threshold dark matter search with CCDs in the DAMIC experiment.
March 9, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar Cosmology with 300,000 Standard Sirens 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.
March 16, 2012 | 12:00 PM | LASR Conference Room | Friday noon seminar Supernova rate by subclass in the local universe Jesse Leaman, Space Science Institute
February 22, 2012 | 12:00 PM | LASR conference room | Special seminar The JEM-EUSO mission: Doing Astronomy by looking down to Earth Toshikazu Ebisuzaki, RIKEN
The idea of looking down onto the surface of the Earth to observe air-showers from space is not new. In fact, John Linsley already in 1979, had proposed to use a space telescope for the observation of UV emission from air-showers. Since then, a few missions were proposed to achieve this next generation technology for the exploration of the high energy universe. Space-based ultra-high energy observatories have important advantages compared with ground detectors: 1) the huge exposure area, 2) the well constrained distance to a shower, 3) the dust-free and cloud-less condition above half of the troposphere, and 4) the almost uniform exposure covering both hemispheres. The JEM-EUSO misson is the first observatory to do astronomy through charged particle channel by looking down to the Earth from the orbit. It will explore the origin of the extreme energy cosmic rays (EECRs ) above 100 EeV and explore the limits of the fundamental physics, through the observations of their arrival directions and energies. A super-wide-Field (60 degrees) telescope with a diameter of about 2.5m looks down the night sky to detect near UV photons (330-400nm, both fluorescent and Cherenkov photons) emitted from the giant airshowers produced by EECRs. The arrival direction map with more than five hundred events will tell us the origin of the EECRs and allow us to identify the EECR sources with known astronomical objects. Neutral components (neutrinos and gamma rays) can also be detected as well, if their fluxes are high enough. The JEM-EUSO mission is planned to be launched by a H2B rocket about 2017 and transferred to ISS by H2 Transfer Vehicle (HTV) and attached to the Exposed Facility external experiment. It is the international mission, in which more than 250 researchers participate from thirteen countries.
January 24, 2012 | 2:00 PM | LASR Conference Room | Open Group seminar First evidence of pep solar neutrinos by direct detection in Borexino 1 Alvaro E. Chavarria, Princeton University
I will report on the first observation of solar neutrinos in the 1.0 - 1.5 MeV range. This result represents the first experimental evidence for pep solar neutrinos and provides the strongest constraint on the CNO neutrino flux to date, a first step toward high-precision tests of solar neutrino oscillations and the resolution of the solar composition problem. This measurement was made possible by the low radioactive background levels in Borexino and by the adoption of novel data analysis techniques for the suppression of cosmogenic 11C.
March 1, 2012 | 3:30 PM | LASR Conference Room | Open Group seminar Disk galaxy assembly as revealed by the evolution of the Tully-Fisher relation Sarah H Miller, Oxford / Caltech
I will present new measures of the rotation curves of disk galaxies to z~1.7, using deep exposures from the DEIMOS and LRIS spectrographs on the Keck telescopes, in combination with multi-band HST imaging. Contrary to previous studies, we show that the stellar mass Tully-Fisher relation is tightly in place at z~1 with similar scatter to that found locally. Furthermore, I will discuss evidence that there is no substantial change in this relation beyond z~1 to z~1.7, and explore the implications for galaxy-scale baryonic and dark matter interaction in a universe with a strikingly similar stellar mass Tully-Fisher relation over two-thirds of its age.