Browsing by Subject "power spectrum"
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Item The Herschel Stripe 82 Survey (HerS): Maps and Early Catalog(2014-02) Viero, M. P.; Asboth, V.; Roseboom, I. G.; Moncelsi, L.; Marsden, G.; Cooper, E. Mentuch; Zemcov, M.; Addison, G.; Baker, A. J.; Beelen, A.; Bock, J.; Bridge, C.; Conley, A.; Devlin, M. J.; Dore, O.; Farrah, D.; Finkelstein, S.; Font-Ribera, A.; Geach, J. E.; Gebhardt, Karl; Gill, A.; Glenn, Jason; Hajian, A.; Halpern, M.; Jogee, S.; Kurczynski, P.; Lapi, A.; Negrello, M.; Oliver, S. J.; Papovich, C.; Quadri, R.; Ross, N.; Scott, D.; Schulz, B.; Somerville, R.; Spergel, D. N.; Vieira, J. D.; Wang, L.; Wechsler, R.; Cooper, E. Mentuch; Finkelstein, S.; Jogee, S.We present the first set of maps and band-merged catalog from the Herschel Stripe 82 Survey (HerS). Observations at 250, 350, and 500 mu m were taken with the Spectral and Photometric Imaging Receiver instrument aboard the Herschel Space Observatory. HerS covers 79 deg(2) along the SDSS Stripe 82 to an average depth of 13.0, 12.9, and 14.8 mJy beam(-1) (including confusion) at 250, 350, and 500 mu m, respectively. HerS was designed to measure correlations with external tracers of the dark matter density field-either point-like (i.e., galaxies selected from radio to X-ray) or extended (i.e., clusters and gravitational lensing)-in order to measure the bias and redshift distribution of intensities of infrared-emitting dusty star-forming galaxies and active galactic nuclei. By locating HerS in Stripe 82, we maximize the overlap with available and upcoming cosmological surveys. The band-merged catalog contains 3.3 x 10(4) sources detected at a significance of >= 3 sigma (including confusion noise). The maps and catalog are available at http://www.astro.caltech.edu/hers/.Item A Second-Order Bias Model For The Logarithmic Halo Mass Density(2012-07) Jee, Inh; Park, Changbom; Kim, Juhan; Choi, Yun-Yong; Kim, Sungsoo S.; Jee, InhWe present an analytic model for the local bias of dark matter halos in a Lambda CDM universe. The model uses the halo mass density instead of the halo number density and is searched for various halo mass cuts, smoothing lengths, and redshift epochs. We find that, when the logarithmic density is used, the second-order polynomial can fit the numerical relation between the halo mass distribution and the underlying matter distribution extremely well. In this model, the logarithm of the dark matter density is expanded in terms of log halo mass density to the second order. The model remains excellent for all halo mass cuts (from M-cut = 3 x 10(11) to 3 x 10(12) h (1) M-circle dot), smoothing scales (from R = 5 h(-1) Mpc to 50h(-1) Mpc), and redshift ranges (from z = 0 to 1.0) considered in this study. The stochastic term in the relation is found to be not entirely random, but a part of the term can be determined by the magnitude of the shear tensor.Item Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Sky Maps, Systematic Errors, and Basic Results(2011-02) Jarosik, N.; Bennett, C. L.; Dunkley, J.; Gold, B.; Greason, M. R.; Halpern, M.; Hill, R. S.; Hinshaw, G.; Kogut, A.; Komatsu, Eiichiro; Larson, D.; Limon, M.; Meyer, S. S.; Nolta, M. R.; Odegard, N.; Page, L.; Smith, K. M.; Spergel, D. N.; Tucker, G. S.; Weiland, J. L.; Wollack, E.; Wright, E. L.; Komatsu, EiichiroNew full-sky temperature and polarization maps based on seven years of data from WMAP are presented. The new results are consistent with previous results, but have improved due to reduced noise from the additional integration time, improved knowledge of the instrument performance, and improved data analysis procedures. The improvements are described in detail. The seven-year data set is well fit by a minimal six-parameter flat Lambda CDM model. The parameters for this model, using the WMAP data in conjunction with baryon acoustic oscillation data from the Sloan Digital Sky Survey and priors on H-0 from Hubble Space Telescope observations, are Omega(b)h(2) = 0.02260 +/- 0.00053, Omega(c)h(2) = 0.1123 +/- 0.0035, Omega(Lambda) = 0.728(-0.016)(+0.015), n(s) = 0.963 +/- 0.012, tau = 0.087 +/- 0.014, and sigma(8) = 0.809 +/- 0.024 (68% CL uncertainties). The temperature power spectrum signal-to-noise ratio per multipole is greater that unity for multipoles l less than or similar to 919, allowing a robust measurement of the third acoustic peak. This measurement results in improved constraints on the matter density, Omega(m)h(2) = 0.1334(-0.0055)(+0.0056), and the epoch of matter-radiation equality, z(eq) = 3196(-133)(+134), using WMAP data alone. The new WMAP data, when combined with smaller angular scale microwave background anisotropy data, result in a 3 sigma detection of the abundance of primordial helium, Y-He = 0.326 +/- 0.075. When combined with additional external data sets, the WMAP data also yield better determinations of the total mass of neutrinos, Sigma m(nu) <= 0.58 eV (95% CL), and the effective number of neutrino species, N-eff = 4.34(-0.88)(+0.86). The power-law index of the primordial power spectrum is now determined to be n(s) = 0.963 +/- 0.012, excluding the Harrison-Zel'dovich-Peebles spectrum by >3 sigma. These new WMAP measurements provide important tests of big bang cosmology.Item Third-Order Perturbation Theory With Nonlinear Pressure(2009-07) Shoji, Masatoshi; Komatsu, Eiichiro; Shoji, Masatoshi; Komatsu, EiichiroWe calculate the nonlinear matter power spectrum using the third-order perturbation theory without ignoring the pressure gradient term. We consider a semirealistic system consisting of two matter components with and without pressure, and both are expanded into the third order in perturbations in a self-consistent manner, for the first time. While the pressured component may be identified with baryons or neutrinos, in this paper we mainly explore the physics of the nonlinear pressure effect using a toy model in which the Jeans length does not depend on time, i.e., the sound speed decreases as a(-1/2), where a is the scale factor. The linear analysis shows that the power spectrum below the so-called filtering scale is suppressed relative to the power spectrum of the cold dark matter. Our nonlinear calculation shows that the actual filtering scale for a given sound speed is smaller than the linear filtering scale by a factor depending on the redshift and the Jeans length. A similar to 40% change is common, and our results suggest that, when applied to baryons, the temperature of the intergalactic medium inferred from the filtering scale observed in the flux power spectrum of Ly alpha forests would be underestimated by a factor of 2, if one used the linear filtering scale to interpret the data. The filtering mass, which is proportional to the filtering scale cubed, can also be significantly smaller than the linear theory prediction especially at low redshift, where the actual filtering mass can be smaller than the linear prediction by a factor of 3. Finally, when applied to neutrinos, we find that neutrino perturbations deviate significantly from linear perturbations even below the free-streaming scales, and thus neutrinos cannot be treated as linear perturbations.Item What Does Cosmology Tell Us About Particle Physics Beyond The Standard Model?(2012-03) Komatsu, E.; Komatsu, EiichiroCosmology demands particle physics beyond the Standard Model: we need to explain the nature of dark matter and dark energy, and the physics of cosmic inflation. Cosmology also provides the tightest upper bound on the sum of neutrino masses, and it seems only a matter of time before we measure the absolute mass of neutrinos, unveiling the neutrino mass hierarchy. It also provides a measurement of the number of relativistic species at the photon decoupling epoch (at which the temperature of the universe is 3000 K). Astronomy and Astrophysics Decadal Survey conducted by USA's National Academy of Sciences has identified these four topics (dark matter, dark energy, inflation and neutrinos) as the most important subjects to study in cosmology over the next decade. In this contribution, we review the current status on these topics, in light of the recent cosmological constraints.