Browsing by Subject "inflationary"

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Bayesian Analysis Of An Anisotropic Universe Model: Systematics And Polarization
(2010-10) Groeneboom, Nicolaas E.; Ackerman, Lotty; Wehus, Ingunn K.; Eriksen, Hans Kristian; Ackerman, Lotty
We revisit the anisotropic universe model previously developed by Ackerman, Carroll, and Wise (ACW), and generalize both the theoretical and computational framework to include polarization and various forms of systematic effects. We apply our new tools to simulated Wilkinson Microwave Anisotropy Probe (WMAP) data in order to understand the potential impact of asymmetric beams, noise misestimation, and potential zodiacal light emission. We find that neither has any significant impact on the results. We next show that the previously reported ACW signal is also present in the one-year WMAP temperature sky map presented by Liu & Li, where data cuts are more aggressive. Finally, we re-analyze the five-year WMAP data taking into account a previously neglected (-i)(l-l')-term in the signal covariance matrix. We still find a strong detection of a preferred direction in the temperature map. Including multipoles up to l = 400, the anisotropy amplitude for the W band is found to be g = 0.29 +/- 0.031, nonzero at 9 sigma. However, the corresponding preferred direction is also shifted very close to the ecliptic poles at (l, b) = (96, 30), in agreement with the analysis of Hanson & Lewis, indicating that the signal is aligned along the plane of the solar system. This strongly suggests that the signal is not of cosmological origin, but most likely is a product of an unknown systematic effect. Determining the nature of the systematic effect is of vital importance, as it might affect other cosmological conclusions from the WMAP experiment. Finally, we provide a forecast for the Planck experiment including polarization.
Fast Estimator Of Primordial Non-Gaussianity From Temperature And Polarization Anisotropies In The Cosmic Microwave Background. II. Partial Sky Coverage And Inhomogeneous Noise
(2008-05) Yadav, Amit P. S.; Komatsu, Eiichiro; Wandelt, Benjamin D.; Liguori, Michele; Hansen, Frode K.; Matarrese, Sabino; Komatsu, Eiichiro
In the recent paper by Yadav and coworkers we described a fast cubic (bispectrum) estimator of the amplitude of primordial non-Gaussianity of local type, f(NL), from a combined analysis of the cosmic microwave background (CMB) temperature and E-polarization observations. In this paper we generalize the estimator to deal with a partial sky coverage as well as inhomogeneous noise. Our generalized estimator is still computationally efficient, scaling as O(N-pix(3/2)) compared to the O(N-pix(5/2)) scaling of the brute- force bispectrum calculation for sky maps with Npix pixels. Upcoming CMB experiments are expected to yield high- sensitivity temperature and E- polarization data. Our generalized estimator will allow us to optimally utilize the combined CMB temperature and E- polarization information from these realistic experiments and to constrain primordial non- Gaussianity.
Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological interpretation
(2011-02) Komatsu, Eiichiro; Smith, K. M.; Dunkley, J.; Bennett, C. L.; Gold, B.; Hinshaw, G.; Jarosik, N.; Larson, D.; Nolta, M. R.; Page, L.; Spergel, D. N.; Halpern, M.; Hill, R. S.; Kogut, A.; Limon, M.; Meyer, S. S.; Odegard, N.; Tucker, G. S.; Weiland, J. L.; Wollack, E.; Wright, E. L.; Komatsu, Eiichiro
The combination of seven-year data from WMAP and improved astrophysical data rigorously tests the standard cosmological model and places new constraints on its basic parameters and extensions. By combining the WMAP data with the latest distance measurements from the baryon acoustic oscillations (BAO) in the distribution of galaxies and the Hubble constant (H-0) measurement, we determine the parameters of the simplest six-parameter Lambda CDM model. The power-law index of the primordial power spectrum is n(s) = 0.968 +/- 0.012 (68% CL) for this data combination, a measurement that excludes the Harrison-Zel'dovich-Peebles spectrum by 99.5% CL. The other parameters, including those beyond the minimal set, are also consistent with, and improved from, the five-year results. We find no convincing deviations from the minimal model. The seven-year temperature power spectrum gives a better determination of the third acoustic peak, which results in a better determination of the redshift of the matter-radiation equality epoch. Notable examples of improved parameters are 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) (68% CL), which benefit from better determinations of the third peak and H-0. The limit on a constant dark energy equation of state parameter from WMAP+BAO+H-0, without high-redshift Type Ia supernovae, is w = -1.10 +/- 0.14 (68% CL). We detect the effect of primordial helium on the temperature power spectrum and provide a new test of big bang nucleosynthesis by measuring Y-p = 0.326 +/- 0.075 (68% CL). We detect, and show on the map for the first time, the tangential and radial polarization patterns around hot and cold spots of temperature fluctuations, an important test of physical processes at z = 1090 and the dominance of adiabatic scalar fluctuations. The seven-year polarization data have significantly improved: we now detect the temperature-E-mode polarization cross power spectrum at 21 sigma, compared with 13 sigma from the five-year data. With the seven-year temperature-B-mode cross power spectrum, the limit on a rotation of the polarization plane due to potential parity-violating effects has improved by 38% to Delta a = -1 degrees.1 +/- 1 degrees.4(statistical) +/- 1 degrees.5(systematic) (68% CL). We report significant detections of the Sunyaev-Zel'dovich (SZ) effect at the locations of known clusters of galaxies. The measured SZ signal agrees well with the expected signal from the X-ray data on a cluster-by-cluster basis. However, it is a factor of 0.5-0.7 times the predictions from "universal profile" of Arnaud et al., analytical models, and hydrodynamical simulations. We find, for the first time in the SZ effect, a significant difference between the cooling-flow and non-cooling-flow clusters (or relaxed and non-relaxed clusters), which can explain some of the discrepancy. This lower amplitude is consistent with the lower-than-theoretically expected SZ power spectrum recently measured by the South Pole Telescope Collaboration.