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

TL;DR

The 7-year WMAP data, combined with other astrophysical measurements, provides precise constraints on cosmological parameters, detects polarization patterns and the SZ effect, and tests fundamental physics such as big bang nucleosynthesis and parity violation.

Contribution

This paper presents the most comprehensive analysis of 7-year WMAP data, including polarization, SZ effect, and cosmological parameter estimation, advancing the understanding of the standard cosmological model.

Findings

Primordial power spectrum index n_s=0.968+-0.012, excluding scale invariance.

Neutrino mass sum < 0.58 eV and N_eff=4.34+0.86-0.88, refining neutrino properties.

Detection of polarization patterns and SZ effect consistent with theoretical models.

Abstract

(Abridged) The 7-year WMAP data and improved astrophysical data rigorously test the standard cosmological model and its extensions. By combining WMAP with the latest distance measurements from BAO and H0 measurement, we determine the parameters of the simplest LCDM model. The power-law index of the primordial power spectrum is n_s=0.968+-0.012, a measurement that excludes the scale-invariant spectrum by 99.5%CL. The other parameters 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. 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+-1.4(stat)+-1.5(syst) degrees. We report significant detections of the 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. However, it is a factor of 0.5 to 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.