Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation

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  • 25 January 2010
Abstract
(Abridged) The 7-year WMAP data and improved astrophysical data rigorously tests the standard cosmological model and its extensions. By combining WMAP with the latest distance measurements from the Baryon Acoustic Oscillations (BAO) and the Hubble constant (H0) measurement, we determine the parameters of the simplest LCDM model. The power-law index of the primordial power spectrum is n_s=0.963+-0.012, a measurement that excludes the scale-invariant spectrum by more than 3-sigma. The other parameters, including those beyond the minimal set, are also improved from the 5-year results. Notable examples of improved parameters are the total mass of neutrinos, sum(m_nu)<0.58eV, and the effective number of neutrino species, N_eff=4.34+0.86-0.88, which benefit from better determinations of the third peak and H0. We detect the effect of primordial helium on the temperature power spectrum and provide a new test of big bang nucleosynthesis. 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. With the 7-year TB power spectrum, the limit on a rotation of the polarization plane due to potential parity-violating effects has improved to Delta(alpha)=-1.1+-1.3(stat)+-1.5(syst) degrees. We report a significant detection of the SZ effect at the locations of known clusters, and show that the current simulations and analytical calculations overestimate the gas pressure, and do not reproduce the observed gas pressure in clusters of galaxies. This result is consistent with the lower-than-expected SZ power spectrum recently measured by the SPT collaboration.

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