Sevenyear Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
Abstract
The combination of sevenyear 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 sixparameter ΛCDM model. The powerlaw index of the primordial power spectrum is n_{s} = 0.968 ± 0.012 (68% CL) for this data combination, a measurement that excludes the HarrisonZel'dovichPeebles spectrum by 99.5% CL. The other parameters, including those beyond the minimal set, are also consistent with, and improved from, the fiveyear results. We find no convincing deviations from the minimal model. The sevenyear temperature power spectrum gives a better determination of the third acoustic peak, which results in a better determination of the redshift of the matterradiation equality epoch. Notable examples of improved parameters are the total mass of neutrinos, ∑m _{ν} < 0.58 eV(95%CL), and the effective number of neutrino species, N _{eff} = 4.34^{+0.86} _{0.88} (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 highredshift 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 sevenyear polarization data have significantly improved: we now detect the temperatureEmode polarization cross power spectrum at 21σ, compared with 13σ from the fiveyear data. With the sevenyear temperatureBmode cross power spectrum, the limit on a rotation of the polarization plane due to potential parityviolating effects has improved by 38% to Δ α =1.1± 1.4° statistical ± 1.5 systematic (68% CL). We report significant detections of the SunyaevZel'dovich (SZ) effect at the locations of known clusters of galaxies. The measured SZ signal agrees well with the expected signal from the Xray data on a clusterbycluster basis. However, it is a factor of 0.50.7 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 coolingflow and noncoolingflow clusters (or relaxed and nonrelaxed clusters), which can explain some of the discrepancy. This lower amplitude is consistent with the lowerthantheoretically expected SZ power spectrum recently measured by the South Pole Telescope Collaboration.
WMAP is the result of a partnership between Princeton University and NASA's Goddard Space Flight Center. Scientific guidance is provided by the WMAP Science Team.
 Publication:

The Astrophysical Journal Supplement Series
 Pub Date:
 February 2011
 DOI:
 10.1088/00670049/192/2/18
 arXiv:
 arXiv:1001.4538
 Bibcode:
 2011ApJS..192...18K
 Keywords:

 cosmic background radiation;
 cosmology: observations;
 dark matter;
 early universe;
 space vehicles;
 Astrophysics  Cosmology and Extragalactic Astrophysics
 EPrint:
 57 pages, 20 figures. Accepted for publication in ApJS. (v2) References added. The SZ section expanded with more analysis. The discrepancy between the KS and Xray derived profiles has been resolved. (v3) New analysis of the SZ effect on individual clusters added (Section 7.3). The LCDM parameters have been updated using the latest recombination history code (RECFAST version 1.5)