KICP Friday Noon Seminars: 2005
DateTalk TitleSpeaker
January 7, 2005A search for physics beyond the Standard Model: measurements of the fine structure constantBrian Odom, Kavli Institute for Cosmological Physics
January 14, 2005From milliKelvin to MegaKelvin: How superconductivity can help elucidate cosmologyTarek Saab
January 21, 2005Supernova Studies and Supernova CosmologyLifan Wang, LBL
January 28, 2005Observing Trans-Planckian Signatures in the Cosmic Microwave BackgroundHiranya Peiris, Kavli Institute for Cosmological Physics
February 4, 2005Unmasking Damped Lya Absorbing GalaxiesHsiao-Wen Chen, MIT
February 18, 2005Looking for an extra dimension with two windows on acceleration and gravitationYong-Seon Song, KICP
February 25, 2005Islands in the Lambda-seaTanmay Vachaspati, Case Western University
March 4, 2005Cosmic strings and high energy physicsArtuu Rajantie
March 11, 2005Measurements of the Temperature and Polarization anistropies with BoomerangBill Jones
March 18, 2005Braneworlds and Beyond: Differentiating Modified Gravity from Dark EnergyArthur Lue, Case Western University
April 1, 2005The future of dark energy measurementsDragan Huterer, Kavli Institute for Cosmological Physics
April 8, 2005Kinematics and Dark Energy From Supernovae at z>1Adam Reiss, StSCI
April 15, 2005Reionization and Early Chemical Enrichment by the First StarsJason Tumlinson, University of Chicago
April 22, 2005The Dark Energy SurveyJames Annis, FNAL
April 29, 2005Measuring the CMB Anisotropies with Bolometers: ACBAR, BICEP, and BeyondChao-Lin Kuo, CalTech
May 6, 2005Precision Cosmology in the Non-linear RegimeJames Taylor, Oxford University
May 13, 2005Cosmic Rays: from the lowest to the highest energiesMaximo Ave, University of Chicago
May 20, 2005Direct Measurements of the Composition of Cosmic RaysJojo Boyle, University of Chicago
May 27, 2005Cluster Density Profiles from Weak Lensing in the SDSSErin Sheldon, Kavli Institute for Cosmological Physics
June 3, 2005Spheroids on Steroids: Insights from a Study of Intracluster LightAnthony Gonzalez, University of Florida
June 10, 2005Twenty-one centimeter radiation and epoch of reionizationXiaomin Wang, Kavli Institute for Cosmological Physics
September 30, 2005Miniquasar feedback before reionizationMichael Kuhlen
October 7, 2005Cosmology with Galaxy ClustersJoseph Mohr
October 14, 2005Just how much information about cosmology does the nonlinear galaxy power spectrum contain?Andrew Hamilton
October 21, 2005Multi-Scale Growth of Cosmic StructureJuna Kollmeier
October 28, 2005New constraints on the extragalactic background light from TeV astronomySimon Swordy, Kavli Institute for Cosmological Physics
November 4, 2005A New look at Dark Matter in the UniverseManoj Kaplinghat
November 11, 2005Constraints on neutrino Physics from cosmology and their impact on world neutrino dataAlessandro Melchiorri
November 18, 2005Science results with SDSS weak lensingRachel Mandelbaum, Princeton University
December 2, 2005 cancelledThis seminar has been cancelledRisa Wechsler, Kavli Instittute for Cosmological Physics

A search for physics beyond the Standard Model: measurements of the fine structure constant
January 7, 2005 | LASR Conference Room | 12:00 PM
Brian Odom, Kavli Institute for Cosmological Physics

I will give an overview of recent measurements of the fine structure constant and of its possible time dependence. The significance of these measurements in terms of searches for physics beyond the standard model will be discussed. I will also present preliminary results for the newest and most precise measurement of the fine structure constant, based on the first fully quantum measurement of the electron magnetic moment, performed at Harvard University.

From milliKelvin to MegaKelvin: How superconductivity can help elucidate cosmology
January 14, 2005 | LASR Conference Room | 12:00 PM
Tarek Saab

Recent great steps taken in the fields of cosmology and astrophysics have lead, inevitably, to new and more detailed sets of questions. X-rays hold the clue to some of the answers by providing diagnostics of the hot inter-stellar gases and plasmas where temperatures reach MegaKelvin (or keV). Superconductors enter the picture by making it possible to satisfy the desire for large, high quality data. In the last few years, detectors based on superconducting technology, have reached maturity and are finding applications in various areas of astrophysics ranging from x-ray spectroscopy to Dark Matter detection. In addition, new concepts based on other low temperature phenomena are being developed and targeted at future experiments. This talk will describe how astrophysics’ desire for higher count rates, energy, timing, and position resolution can be satisfied with detectors operating at mK temperatures.

Supernova Studies and Supernova Cosmology
January 21, 2005 | LASR Conference Room | 12:00 PM
Lifan Wang, LBL

In recent years, Type Ia supernovae (SNIa) have emerged as the most precise cosmological distance indicators. I will discuss recent observational progresses on the studies of the nature of SNIa, based largely on a multi-year effort of spectropolarimetry observations collected at the ESO-VLT. These observations reveal that SNIa ejecta are highly aspherical at the highest velocity, whereas the asphericity decreases at layer with decreasing expansion velocities. There are indications that the asphericity is dominated by chemical inhomogeneities of the size of the photosphere at the time of optical maximum (~11,000 km/sec). There are strong evidences of the existence of detached clumpy layers, likely enriched in calccium, moving at the highest velocities (~22,000 km/sec) in some SN Ia ejecta. These new findings are not expected in popular models of SN Ia explosions. They provide important clues to the physics of SN Ia explosions. For cosmological applications, I will present recent results using the Color-MAGnitude Intercept Calibration (CMAGIC) of SN Ia. I will discuss future projects of SN Ia observations that aim to obtain a significant sample of SNIa with spectropolarimetry data. I will also discuss the prospects of routine discovery of gravitationally lensed SNIa, and the use of them as cosmological probes.

Observing Trans-Planckian Signatures in the Cosmic Microwave Background
January 28, 2005 | LASR Conference Room | 12:00 PM
Hiranya Peiris, Kavli Institute for Cosmological Physics

I will examine the constraints cosmological observations can place on any trans-Planckian corrections to the primordial spectrum of perturbations underlying the anisotropies in the Cosmic Microwave Background. Using a specific "toy model", I will present a case study for the sort of constraints one could hope to apply on a well-motivated model of trans-Planckian physics from future high-precision CMB data. Our results show that the amplitude of the tensor perturbations is directly correlated with the detectability of any trans-Planckian modulation in the primordial power spectrum. This is likely to be true for any trans-Planckian modulation in the paradigm of slow-roll inflation.

Unmasking Damped Lya Absorbing Galaxies
February 4, 2005 | LASR Conference Room | 12:00 PM
Hsiao-Wen Chen, MIT

I will present current results from searching for galaxies giving rise to damped DLA absorbers (DLAs) at z<1. Using 14 galaxies that are known to produce DLA features in the spectra of background QSOs, I will show that intermediate-redshift galaxies possess large HI envelope out to 24-30 h^{-1} kpc radius. In addition, the photometric and spectral properties of these galaxies confirm that DLA galaxies are drawn from the typical field population, and not from a separate population of low surface brightness or dwarf galaxies. Comparisons of the ISM abundances of the DLA galaxies and the metallicities of the absorbers at large galactic radii suggest that some DLAs originate in the relatively unevolved outskirts of galactic disks. An abundance profile characterized by a radial gradient of -0.041+/-0.012 dex per kiloparsec (or equivalently a scale length of 10.6 h^{-1} kpc) is found from galactic center to 30 h^{-1} kpc radius based on an ensemble of six galaxy-DLA pairs. Finally adopting this abundance gradient and known N(HI) profiles of nearby galaxies, I will show that the on-average low metal content of the DLA population can arise naturally as a combination of gas cross-section selection and metallicity gradients commonly observed in local disk galaxies.

Looking for an extra dimension with two windows on acceleration and gravitation
February 18, 2005 | LASR Conference Room | 12:00 PM
Yong-Seon Song, KICP

The cosmic acceleration was discovered in one of the brane-based models as well as dark energy model. Growth factors are different in the two models when one adjusts parameters to get nearly identical H(z). The two models could be distinguished with independent determinations of both geometrical factors and the growth factors. Cosmic shear due to gravitational lensing, can be used to simultaneously determine the distance-redshift relation, D(z), and the rate of growth of density contrasts, g(z). Both of these functions are sensitive probes of the acceleration. Their simultaneous determination allows for a consistency test and provides sensitivity to physics beyond the standard dark energy paradigm.

Islands in the Lambda-sea
February 25, 2005 | RI 480 | 12:00 PM
Tanmay Vachaspati, Case Western University

We propose an alternate cosmological model in which our observable universe is an island in a cosmological constant sea. Initially the universe is filled with cosmological constant of the currently observed value but is otherwise empty. In this eternal or semi-eternal de Sitter spacetime, we show that local quantum fluctuations (upheavals) can violate the null energy condition and create islands of matter. The perturbation spectra of quantum fields other than that responsible for the upheaval, are shown to be scale invariant. With further cosmic evolution the island disappears and the local universe returns to its initial cosmological constant dominated state.

Cosmic strings and high energy physics
March 4, 2005 | LASR Conference Room | 12:00 PM
Artuu Rajantie

I will discuss the formation of topological defects such as cosmic strings in the early universe. Depending on physics at very high energies, defects may be formed by different mechanisms. I will review these mechanism, and show that they have certain distinct consequences in the properties and distribution of the produced defects. Astronomical observation of cosmic strings would therefore give us direct information about very high energy physics.

Measurements of the Temperature and Polarization anistropies with Boomerang
March 11, 2005 | LASR Conference Room | 12:00 PM
Bill Jones

Braneworlds and Beyond: Differentiating Modified Gravity from Dark Energy
March 18, 2005 | LASR Conference Room | 12:00 PM
Arthur Lue, Case Western University

The nature of the fuel that drives today's cosmic acceleration is an open and tantalizing mystery. I entertain the suggestion that the acceleration is not the manifestation of yet another new ingredient in the cosmic gas tank, but rather our first real lack of understanding of gravitational physics. I discuss first an intriguing braneworld model (Dvali-Gabadadze-Porrati) and extend the discussion to a more general context, addressing questions about modified-gravity cosmologies and dark energy at astrophysically interesting, and even solar sytem, scales, with these distinctions being subject to imminent observational discrimination.

The future of dark energy measurements
April 1, 2005 | LASR Conference Room | 12:00 PM
Dragan Huterer, Kavli Institute for Cosmological Physics

Evidence for the existence of some form of dark energy -- a smooth component that causes the accelerated expansion of the universe and contributes about 70% of the total energy density -- is by now very solid. Despite thousands of published papers on the topic, however, very little progress has been made in understanding its nature and the underlying physical mechanism. In this talk I describe the prospects of several methods to measure the macroscopic properties of dark energy within the next decade. In addition to type Ia supernovae, these include weak and strong gravitational lensing, number counts of clusters of galaxies, and cosmic microwave background anisotropies. I particularly concentrate on weak gravitational lensing, describing the recent progress and challenges in controlling the systematic errors. Considering the expected sensitivity of space-based experiments that will perform these measurements, I comment on the prospects for the overall advancement of our understanding of dark energy.

Kinematics and Dark Energy From Supernovae at z>1
April 8, 2005 | LASR Conference Room | 12:00 PM
Adam Reiss, StSCI

Type Ia supernovae (SNe~Ia) provide the only direct evidence for an accelerating universe and the existence of dark energy. We are in the third year of the first space-based search and follow-up campaign to find SNe Ia at z>1 using the Hubble Space Telescope to further explore the kinematics of the expanding Universe and to characterize the nature of dark energy.

Reionization and Early Chemical Enrichment by the First Stars
April 15, 2005 | LASR Conference Room | 12:00 PM
Jason Tumlinson, University of Chicago

The first stars hold our interest for their uniqueness and for their potential importance to galaxy formation, chemical enrichment, and feedback on the IGM. I will review recent progress in understanding the intrinsic properties and cosmological importance of zero-metallicity stars. I will discuss insights into the mass function of early stars drawn from observations of reionization at high redshift and their nucleosynthetic "fossil remnants" preserved in the most metal-poor Galactic stars. I will then describe ongoing work to integrate a detailed Galactic chemical evolution model into the CDM picture of the formation of galaxies. This new model uses all the relevant observed phenomena to jointly constrain the mass function, metallicity evolution, and epoch over which metal free stars could have formed. Finally, I will comment on the long term prospects for finding the first stars from space and from the ground.

The Dark Energy Survey
April 22, 2005 | RI 480 | 12:00 PM
James Annis, FNAL

The Dark Energy Survey is a project that aims to map 5000 square-degrees near the South Galactic Cap in g,r,i,z at i > 24 starting in 2009. The survey aims to measure w to <= 5% using 4 independent techniques: cluster count evolution, weak lensing, galaxy angular power spectra, and supernovae. The talk will discuss the project science goals, the Blanco 4m telescope and the new 500 megapixel camera we are building, the LBL deep depletion CCDs, how the survey is to be conducted.

Measuring the CMB Anisotropies with Bolometers: ACBAR, BICEP, and Beyond
April 29, 2005 | LASR Conference Room | 12:00 PM
Chao-Lin Kuo, CalTech

I will discuss three topics in this talk, first by reporting the latest results from the Arcminute Cosmology Bolometer Array Receiver (ACBAR). Significant improvements in sensitivity over the previous data release have been achieved by a combination of more efficient analysis techniques and the inclusion of more data. Together with the CBI measurements at lower photon frequencies, and the WMAP results on large angular scales, the joint ACBAR/CBI/WMAP power spectrum represents the current best knowledge of the temperature anisotropy between l=2 and 3000. I will then give an update on the status of the BICEP experiment (Background Imaging of Cosmological Extragalactic Polarization). BICEP is operating at 100 GHz and 150 GHz at angular resolutions of 1.0 and 0.7 degree, with an array of 98 polarization-sensitive detectors. The experiment is targeting the B-mode polarization in the CMB, which is an imprint of the primordial gravitational background radiation. It is scheduled to start observing at the South Pole station later this year. Finally, I will describe the detector development efforts at JPL/Caltech, with the emphasis on the antenna-coupled transition-edge-sensor (TES) technology for next generation CMB experiments.

Precision Cosmology in the Non-linear Regime
May 6, 2005 | LASR Conference Room | 12:00 PM
James Taylor, Oxford University

Current precision cosmology relies on measurements of the average evolution of the universe and of the amplitude of small, localized fluctuations around this average as long as they are still growing linearly. The subsequent non-linear phase of growth, leading to the formation of virialized dark matter halos, is harder to understand analytically but has been shown to produce simple robust patterns in extensive numerical simulations of structure formation. I will discuss several possible next-generation tests of cosmology based on the internal properties of dark matter halos, including their concentration, triaxiality, spin and substructure.

Cosmic Rays: from the lowest to the highest energies
May 13, 2005 | LASR Conference Room | 12:00 PM
Maximo Ave, University of Chicago

Many puzzles are associated with the observed properties of the CRs from very high energies, those above 10^15 eV, and up to the highest energy ones exceeding 10^20 eV. In particular, we would like to know what causes the spectral changes observed and the changes in composition as a function of energy. We will review the status of the observations and discuss the recent developments on theoretical models. Finally, we will focus on the high energy end of the spectrum (above 10^19 eV), an energy regime that is being scanned by the Pierre Auger Observatory. Some of the recent results will be presented.

Direct Measurements of the Composition of Cosmic Rays
May 20, 2005 | LASR Conference Room | 12:00 PM
Jojo Boyle, University of Chicago

While the overall cosmic-ray spectrum covers an enormous range of energies, extending beyond 10^20 eV per particle, details on the composition of the cosmic rays are known for only a fraction of this range. Yet without information on the abundances and energy spectra of the individual cosmic-ray components, conclusions about the sources of these particles, and of their acceleration and transport through the Galaxy, remain tentative and controversial. Currently, measurements of the energy spectra and absolute intensities of these individual species extend to only a few thousand GeV/amu for primary nuclei and ~200 GeV/amu for secondary nuclei. These measurements support a model in which all cosmic-ray nuclei are accelerated with the same differential energy spectrum which is consistent with that from acceleration in strong shocks, probably supernovae. In an attempt to confirm this expectation and to find experimental clues for the origin of the cosmic rays at still higher energies I will report on two current balloon borne cosmic ray detectors, TRACER and CREAM, that have been developed at the University of Chicago. TRACER is designed to measure the energy spectra of primary nuclei Oxygen to Iron (Z=8->26) over the range 0.5 - >10,000 GeV/amu. TRACER was successfully flown from McMurdo, Antarctica in December 2003. CREAM can detect Protons to Iron (Z=1->26) and had a record-breaking 42-day Antarctic flight in 2004/05. Our goal with CREAM is the determination of the ratio of secondary to primary nuclei towards 1,000 GeV/amu. Combining results from TRACER and CREAM will place severe constraints on existing models for the sources of these cosmic-ray particles, and of their acceleration and transport through the Galaxy.

Cluster Density Profiles from Weak Lensing in the SDSS
May 27, 2005 | RI 480 | 12:00 PM
Erin Sheldon, Kavli Institute for Cosmological Physics

I will show the latest weak lensing results from the Sloan Digital Sky Survey. We use lensing to constrain cluster density profiles in a model-independent way. We compare the measurements to "universal" mass profiles from simulations. We also constrain the mean mass-richness relation at the ~10% level over a wide range of cluster masses. I will discuss how this mass calibration can be used to constrain cosmology. I will also discuss how the density profile on scales of tens of Mpc, far outside the virial radius, can be used to constrain bias and cosmology.

Spheroids on Steroids: Insights from a Study of Intracluster Light
June 3, 2005 | LASR Conference Room | 12:00 PM
Anthony Gonzalez, University of Florida

I present a unifying description of the structural and kinematic properties of all spheroids embedded in dark matter halos. The intracluster stars (ICS) in galaxy clusters define spheroids that are typically 100 times the size of normal elliptical galaxies. Our analysis of these spheroids demonstrates that they lie on a "fundamental plane" as tight as that defined by normal ellipticals, but with a different slope. We attribute the difference primarily to a corresponding change in M/L within the effective radius. By expressing the M/L term in the simple derivation of the fundamental plane in terms of the velocity dispersion, and requiring that the behavior of that term mimic the observed relation between the two quantities, we simultaneously fit a surface to ellipticals, BCGs, and the ICS. The new relation fits spheroids that span three decades in effective radius. I will also show that the ICS are a significant source of metals for the intracluster medium.

Twenty-one centimeter radiation and epoch of reionization
June 10, 2005 | LASR Conference Room | 12:00 PM
Xiaomin Wang, Kavli Institute for Cosmological Physics

The observation of twenty-one centimeter radiation is emerging as a powerful tool to explore the end of cosmic dark age and the epoch of reionization. I will describe the mechanism, the emission power spectra, and what it can tell us about the early Universe. What we are able to learn from 21cm observations are limited by our ability to lift various contaminations from the observed signal, such as astrophysical foregrounds, noise, and redshift space distortions, etc. I will present our approach to some of these issues. I will also discuss the aspects of some upcoming and future 21cm experiments.

Miniquasar feedback before reionization
September 30, 2005 | LASR Conference Room | 12:00 PM
Michael Kuhlen

I will present results from recent AMR cosmological hydro simulations modeling the radiative feedback from an early miniquasar. Accreting intermediate mass black holes are powerful sources of X-ray radiation, which is able to penetrate the cold, neutral medium before reionization and significantly alter its thermal and chemical properties. I will discuss the miniquasar's effect on the proto-IGM's temperature, clumping factor, ionization fraction, and molecular hydrogen abundance, and comment on the possibility of observing these effects via redshifted 21cm emission against the CMB.

Cosmology with Galaxy Clusters
October 7, 2005 | RI 480 | 12:00 PM
Joseph Mohr

Just how much information about cosmology does the nonlinear galaxy power spectrum contain?
October 14, 2005 | LASR Conference Room | 12:00 PM
Andrew Hamilton

The technology for measuring cosmological parameters from galaxy power spectra in the linear regime is now well-developed. Yet much of the information in real galaxy surveys potentially lies at smaller, non-linear scales. Can information about cosmology be extracted from non-linear clustering? In this talk I show how to answer this question quantitatively, from measurements of the Fisher information from simulations of large scale structure. The results are surprising: at translinear scales there is an order of magnitude less information than one might have expected, whereas at just-virialized scales there is an order of magnitude more information than one might have expected. The results impel a revision of one's (mine, anyway) thinking about clustering at non-linear scales.

Multi-Scale Growth of Cosmic Structure
October 21, 2005 | LASR Conference Room | 12:00 PM
Juna Kollmeier

I will discuss the growth of structure from black holes to the intergalactic medium. Turning density fluctuations into galaxies and black holes is difficult and many outstanding issues remain to be solved. I will discuss three separate ways to attack this problem on different physical scales: IGM-Galaxy correlations on small and large scales, fluorescent Lyman alpha emission from gaseous structures produced in LambdaCDM hydrodynamic simulations, and black hole mass and Eddington ratio measurements with the AGN and Galaxy Evolution Survey.

New constraints on the extragalactic background light from TeV astronomy
October 28, 2005 | LASR Conference Room | 12:00 PM
Simon Swordy, Kavli Institute for Cosmological Physics

New results from TeV observations from the most distant AGN yet observed have provided some constraints on the intensity of the EBL which are becoming interesting.

A New look at Dark Matter in the Universe
November 4, 2005 | LASR Conference Room | 12:00 PM
Manoj Kaplinghat

Supersymmetric theories predict two kinds of dark matter. One kind, cold dark matter, is made up of non-relativistic weakly interacting massive particles (WIMPs). The other kind has a non-thermal distribution and they are populated by decays of WIMPs in the early universe with a natural lifetime of about a month. This model of dark matter from early decays may be distinguished from the cold dark matter model by observations of structure on scales smaller than about a megaparsec. They may not suffer from problems on the small scales that seem to beset the cold dark matter model.

Constraints on neutrino Physics from cosmology and their impact on world neutrino data
November 11, 2005 | LASR Conference Room | 12:00 PM
Alessandro Melchiorri

We demonstrate that Cosmic Microwave Background anisotropies and galaxy clustering data yield an indication for primordial anisotropies in the cosmological Neutrino Background. We then derive several cosmological bounds on Neutrino Physics. The results are discussed and compared with neutrino oscillation data and upper limits on the effective neutrino mass from beta decay experiments.

Science results with SDSS weak lensing
November 18, 2005 | LASR Conference Room | 12:00 PM
Rachel Mandelbaum, Princeton University

The SDSS has proven to be an excellent dataset for exploring various problems in astrophysics and cosmology using weak lensing, with the highest lensing signal to noise to date and spectroscopic redshifts for lens galaxies, which simplifies theoretical interpretation by allowing us to compute signal as a function of transverse separation rather than angle. In this talk, I will describe our new Reglens reduction method that is used to measure galaxy shapes, discuss constraints on systematic errors, and describe several interesting science results that have resulted from it. Recently, we have placed constraints on dark matter halo ellipticity, and detected intrinsic ellipticity-density alignments that may be important contaminants of current and future weak lensing surveys. I will also describe ongoing work such as a measurement of the dark matter power spectrum using a combination of galaxy-shear cross-correlation and galaxy-galaxy autocorrelation techniques; a study of the relationship between stellar masses, luminosities, and dark matter halo masses as a function of morphology and local environment; and the determination of average halo profiles using the lensing signal around field galaxies.

This seminar has been cancelled
December 2, 2005 cancelled | LASR Conference Room | 12:00 PM
Risa Wechsler, Kavli Instittute for Cosmological Physics

CANCELLED