Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session C12: Cosmic Microwave Background and Cosmology |
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Sponsoring Units: DAP Chair: Michael Turner, Kavli Institute for Cosmological Physics, University of Chicago Room: Plaza Court 2 |
Saturday, May 2, 2009 1:30PM - 1:42PM |
C12.00001: Atacama B-mode Search: Scientific Motivations and Design Overview Ki Won Yoon The Atacama B-mode Search (ABS) is a new experiment designed to characterize the polarization of the cosmic microwave background (CMB) to unprecedented levels at degree angular scales, where the signature of primordial gravitational waves from an inflationary epoch in the early universe is expected to peak. ABS employs a novel optical design using a cryogenically-cooled crossed-Dragone reflective telescope coupled to an array of $\sim $200 direct-machined feedhorns, each of which in turn couples the incoming radiation onto a ``polarimeter-on-a-chip'' consisting of a planar ortho-mode transducer, microstrip band-defining filters, and a pair of transition-edge sensors (TES) that measure both polarizations simultaneously. The array will be initially designed for operation at 145 GHz. ABS is currently scheduled to begin observation in the Atacama Desert of Chile in late 2009. [Preview Abstract] |
Saturday, May 2, 2009 1:42PM - 1:54PM |
C12.00002: ACTpol: An experiment to measure small angular scale polarization anisotropies in the CMB Michael Niemack Small angular scale cosmic microwave background (CMB) polarization measurements can be used to constrain the neutrino mass and a precise measurement of the CMB gravitational lensing spectrum amplitude will improve constraints on the dark energy equation of state. In addition, these measurements will provide detailed characterization of foregrounds that are expected to contaminate large angular scale searches for the predicted polarization signature of gravitational waves during the epoch of inflation. The Atacama Cosmology Telescope (ACT) is a six-meter telescope on the Atacama plateau, Chile that was built to characterize the cosmic microwave background (CMB) on small angular scales. Since 2007 ACT has been used to measure the temperature anisotropies in the CMB in three bands between 140 - 300 GHz with arcminute resolution. We report on the design of a new instrument for ACT that will add polarization sensitivity to the telescope (ACTpol). The design includes new optics to couple to a 150 GHz polarization sensitive camera under development at NIST that comprises a large array of feedhorn coupled polarimeters. The polarimeters are planar superconducting ortho-mode transducers combined with stub filters and bolometric transition-edge sensors to measure the radiation. [Preview Abstract] |
Saturday, May 2, 2009 1:54PM - 2:06PM |
C12.00003: ABSTRACT WITHDRAWN |
Saturday, May 2, 2009 2:06PM - 2:18PM |
C12.00004: Evidence for a Primordial Magnetic Field from the CMB Polarization and Power Spectra Grant Mathews, Dai Yamazaki, Toshitaka Kajino, Kiyotomo Ichiki Magnetic fields play an important role in many astronomical phenomena on various cosmological scales. In particular, a primordial magnetic field (PMF) could manifest itself in the cosmic microwave background (CMB) temperature and polarization anisotropies, and also in the formation of large- scale structure. We have developed a new high-precision theoretical framework in which to calculate the CMB temperature and polarization anisotropies, along with the matter power spectrum generated when a power-law PMF is present at the epoch of photon last-scattering. We discuss prelimminary evidence that the existing accumulated data on both the matter and CMB power spectra on small angular scales fixes both the upper and lower limits to the magnetic field strength and power spectral index. We find parameter values for the amplitude of the PMF of 2.248 nG $<$ B $<$ 3.055 nG and a spectral index in the range -2.387 $<$ n $<$ -1.367 at the present scale of 1 Mpc. This may be the first direct evidence that a primordial magnetic field was indeed present during the big bang. [Preview Abstract] |
Saturday, May 2, 2009 2:18PM - 2:30PM |
C12.00005: ABSTRACT WITHDRAWN |
Saturday, May 2, 2009 2:30PM - 2:42PM |
C12.00006: ABSTRACT WITHDRAWN |
Saturday, May 2, 2009 2:42PM - 2:54PM |
C12.00007: Probing the Dark Matter-Galaxy Formation Connection with Lyman Alpha Emitting Galaxies Eric Gawiser I will describe how our understanding of cosmological structure formation is used to probe the dark matter properties of high-redshift galaxies and to identify their present-day descendants. We studied the clustering properties and multiwavelength spectral energy distributions of a complete sample of 162 Lyman Alpha Emitting (LAE) galaxies at redshift $z=3.1$ discovered in deep narrow-band imaging of the MUSYC survey. The LAEs exhibit a moderate clustering bias of $b=1.7$, which implies median dark matter halo masses of $10^{11}$ M$_\odot$. The evolution of dark matter halo mass with redshift predicts that $z=3.1$ LAEs evolve into typical present-day galaxies like the Milky Way, whereas other high-redshift galaxy populations, including Lyman Break Galaxies and Active Galactic Nuclei, typically evolve into more massive galaxies. Hence the Lyman Alpha Emitting galaxies that we have discovered represent our first direct knowledge of the progenitors of galaxies like the Milky Way seen when the universe was only 2 Gyr in age. \\ References: Gawiser et al. 2007 (Astrophysical Journal 671, 278), Francke et al. 2008 (Astrophysical Journal Letters 673, 13) [Preview Abstract] |
Saturday, May 2, 2009 2:54PM - 3:06PM |
C12.00008: Gravitational Wave Propagation in Perturbed FRW Cosmologies: The Gravitational Integrated Sachs-Wolfe Effect Pablo Laguna, Shane Larson, Nicolas Yunes Gravitational waves carry with them in exquisite detail knowledge of the source structure. For the case of inspiraling binary systems, the radiation carries with it information of the component masses and spins, the orbital angular momentum, energy and orientation with respect to the line-of-sight and the system's luminosity distance. For sources at large cosmological distances, gravitational waves will carry in addition an imprint of the spacetime background thorough which they propagate. The dominant effect is the cosmological redshift due to the overall expansion of the Universe. We present results of the secondary cosmological effect on gravitational waves due to intervening inhomogeneities, in other words, the gravitational counterpart of the integrated Sachs-Wolfe effect associated with CMBR photons. [Preview Abstract] |
Saturday, May 2, 2009 3:06PM - 3:18PM |
C12.00009: Bolometric Interferometry for Cosmic Microwave Background Polariztion Measurements Siddharth Malu CMB studies are now~a data-rich field in astrophysics. The power spectrum of CMB is well measured and cosmological models have been characterized and polarization has been detected in the CMB. All results fit well within and are explained well by the inflationary paradigm. But current evidence for inflation is indirect. The next generation of CMB experiments will aim at providing the most direct evidence for inflation through the detection of B-modes in CMB polarization. Despite improvements in experimental techniques, it is as yet unclear what configuration and approach a CMB polarization experiment should adopt, in view of lack of information about polarization foregrounds and instrument systematic effects. We describe a novel approach to these measurements, called bolometric interferometry, which avoids many of the systematic errors found in imaging systems. In particular, we describe a prototype, the Millimeter-wave Bolometric Interferometer (MBI). We present a few promising approaches from our collaboration (BRAIN/MBI) and discuss plans for feasibility studies for detecting CMB polarization foregrounds and signals with adding interferometers. [Preview Abstract] |
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