Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session Y5: The CMB and Reionization |
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Sponsoring Units: DAP Chair: Simeon Bird, Johns Hopkins University Room: Virginia B |
Tuesday, January 31, 2017 1:30PM - 1:42PM |
Y5.00001: The Cosmology Large Angular Scale Surveyor (CLASS): instrument and survey status Joseph Eimer The Cosmology Large Angular Scale Surveyor (CLASS) is an array of four telescopes that observes the polarization of the cosmic microwave background from the Atacama Desert in Chile. From this site, CLASS surveys 70\% of the sky at four frequency bands centered at 38, 93, 148, and 217 GHz respectively. By targeting the polarized signal on the largest scales, CLASS uniquely aims to characterize the E and B-mode power spectra on both the reionization and recombination scales. Simulations, including systematics and foregrounds, have shown the CLASS strategy of combining large sky coverage, front-end polarization modulation, and high sensitivity enables characterization of inflationary gravitational waves at all relevant angular scales to the r=0.01 level, measurements of the optical depth to reionization to the cosmic-variance-limit, and improved constraints on the mass of neutrinos. The first telescope of the CLASS array, observing at 38 GHz, achieved first light in May 2016. Here I review the objectives, strategy and architecture of the CLASS experiment and give an update on the survey. [Preview Abstract] |
Tuesday, January 31, 2017 1:42PM - 1:54PM |
Y5.00002: Isotropy-violation tests and turbulence for CMB B-mode foregrounds Kevin Huffenberger, Aditya Rotti, David Collins Isotropy-violation tests can be used to assess the level of foreground contamination along different lines of sight. First application of an isotropy-violation test on Planck 353 GHz B-mode polarization data indicated a potential foreground source in the BICEP patch. We also discuss ongoing efforts to characterize the polarization properties of galactic dust via hydrodynamical simulations. [Preview Abstract] |
Tuesday, January 31, 2017 1:54PM - 2:06PM |
Y5.00003: CMB lensing from SPT+Planck and cross-correlations Yuuki Omori The South Pole Telescope (SPT) SZ survey has observed 2500 square degrees of the Cosmic Microwave Background (CMB) to high accuracy down to 1 arcminute resolution at 150GHz. The Planck satellite has also observed the same patch of the CMB sky at 143GHz, but the two experiments were designed to measure temperature anisotropies optimally at different angular scales. By combining data from these two experiments, we are able to produce a temperature map that has an improved signal-to-noise ratio at all scales. This combined temperature map is used to produce a CMB weak lensing map, which we use for cosmological parameter and cross-correlation analyses. In particular, the SPT footprint has significant overlap with the Dark Energy Survey (DES) observing region, which allows us to cross-correlate the CMB lensing map with galaxy density and galaxy shear measurements obtained by DES. In this talk, I will present the SPT+Planck combining procedure, the CMB lensing reconstruction pipeline, tests performed to verify the lensing map, and finally the cross-correlation measurements. [Preview Abstract] |
Tuesday, January 31, 2017 2:06PM - 2:18PM |
Y5.00004: Velocity correlations in simulations and observations Yuyu Wang, Christopher Rooney, Hume Feldman, Richard Watkins We present an analysis of the two-point cosmic velocity correlation function. We calculate the correlations of the Cosmicflows catalogues and estimate the errors using the Millennium N-body simulations. We estimate the correlation coherence length, and combine the velocity correlation function expectations from linear theory to constrain the cosmological parameters $\Gamma$ and $\beta$. Using the maximum likelihood method, we find a value of $\Gamma=0.195^{+0.08}_{-0.045}$ (95\% CL) that is consistent with the Planck results. [Preview Abstract] |
Tuesday, January 31, 2017 2:18PM - 2:30PM |
Y5.00005: ABSTRACT WITHDRAWN |
Tuesday, January 31, 2017 2:30PM - 2:42PM |
Y5.00006: Magnetizing the Universe during the Epoch of Reionization Daegene Koh, John Wise Magnetic fields are speculated to affect the collapse dynamics in early star formation to influence the IMF, which may be imprinted in the local metal-poor population. These fields arise by the amplification of primordial fields during the formation of the first (Pop III) and from their feedback. We study the former using MHD simulations with a uniform seed field from cosmological initial conditions to the formation and supernova of a Pop III star. We find that a weak seed field can be amplified to $\mu$G at the density peak and by a factor of 100 around the shell of the supernova shock. We also explored the dynamics of metal-poor mini-halos, enriched by Pop III supernova, in varying metallicities and Lyman-Werner flux to produce a fit for the minimum collapse mass. Furthermore, Pop III stars are significant drivers of reionization at high redshift (z$>$10). We use semi-numeric methods including Pop III stars as ionizing sources and find smaller characteristic HII bubbles sizes while calculating an optical depth, $\tau_e$ = 0.0569, consistent with the latest results from Planck. The resulting ionization fields can efficiently model the ionizing UV background in cosmological simulations. These results are essential to building a full MHD simulation of the first galaxies. [Preview Abstract] |
Tuesday, January 31, 2017 2:42PM - 2:54PM |
Y5.00007: Simulating Cosmic Reionization and Its Observable Consequences Paul Shapiro I summarize recent progress in modelling the epoch of reionization by large- scale simulations of cosmic structure formation, radiative transfer and their interplay, which trace the ionization fronts that swept across the IGM, to predict observable signatures. Reionization by starlight from early galaxies affected their evolution, impacting reionization, itself, and imprinting the galaxies with a memory of reionization. Star formation suppression, e.g., may explain the observed underabundance of Local Group dwarfs relative to N-body predictions for Cold Dark Matter. I describe CoDa ("Cosmic Dawn"), the first fully-coupled radiation-hydrodynamical simulation of reionization and galaxy formation in the Local Universe, in a volume large enough to model reionization globally but with enough resolving power to follow all the atomic-cooling galactic halos in that volume. A 90 Mpc box was simulated from a constrained realization of primordial fluctuations, chosen to reproduce present-day features of the Local Group, including the Milky Way and M31, and the local universe beyond, including the Virgo cluster. The new RAMSES-CUDATON hybrid CPU-GPU code took 11 days to perform this simulation on the Titan supercomputer at Oak Ridge National Laboratory, with 4096-cubed N-body particles for the dark matter and 4096-cubed cells for the atomic gas and ionizing radiation. [Preview Abstract] |
Tuesday, January 31, 2017 2:54PM - 3:06PM |
Y5.00008: CMB B-mode Polarization Measurements and constraints on Primordial Gravitational Waves from the BICEP/Keck Program at South Pole John Kovac The BICEP/Keck Array cosmic microwave background (CMB) polarization experiments located at the South Pole are a series of small-aperture refracting telescopes designed to probe the degree-scale B-mode signature of primordial gravitational waves. These highly-targeted experiments have produced the world's deepest maps of CMB polarization, leading to the most stringent constraints on the tensor-to-scalar ratio to date: r < 0.09 from B-modes alone, and r < 0.07 in combination with other datasets. These limits are rapidly improving with ongoing measurements at the multiple frequencies needed to separate Galactic foregrounds from the CMB, and in combination with higher-resolution experiments to remove B-modes induced by gravitational lensing. I will review the current status of measurements and results, and will discuss the challenges that will be confronted as measurements reach sensitivities to primordial gravitational waves at a level r < 0.01 and below within the next several years. [Preview Abstract] |
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