FiveYear Wilkinson Microwave Anisotropy Probe Observations: Cosmological Interpretation
Abstract
The Wilkinson Microwave Anisotropy Probe (WMAP) 5year data provide stringent limits on deviations from the minimal, sixparameter Λ cold dark matter model. We report these limits and use them to constrain the physics of cosmic inflation via Gaussianity, adiabaticity, the power spectrum of primordial fluctuations, gravitational waves, and spatial curvature. We also constrain models of dark energy via its equation of state, parityviolating interaction, and neutrino properties, such as mass and the number of species. We detect no convincing deviations from the minimal model. The six parameters and the corresponding 68% uncertainties, derived from the WMAP data combined with the distance measurements from the Type Ia supernovae (SN) and the Baryon Acoustic Oscillations (BAO) in the distribution of galaxies, are: Ω_{ b } h ^{2} = 0.02267^{+0.00058} _{0.00059}, Ω_{ c } h ^{2} = 0.1131 ± 0.0034, Ω_{Λ} = 0.726 ± 0.015, n_{s} = 0.960 ± 0.013, τ = 0.084 ± 0.016, and ∆_{R}^2 = (2.445± 0.096)× 10^{9} at k = 0.002 Mpc^{1}. From these, we derive σ_{8} = 0.812 ± 0.026, H _{0} = 70.5 ± 1.3 km s^{1} Mpc^{1}, Ω_{ b } = 0.0456 ± 0.0015, Ω_{ c } = 0.228 ± 0.013, Ω_{ m } h ^{2} = 0.1358^{+0.0037} _{0.0036}, z _{reion} = 10.9 ± 1.4, and t _{0} = 13.72 ± 0.12 Gyr. With the WMAP data combined with BAO and SN, we find the limit on the tensortoscalar ratio of r < 0.22(95%CL), and that n_{s} > 1 is disfavored even when gravitational waves are included, which constrains the models of inflation that can produce significant gravitational waves, such as chaotic or powerlaw inflation models, or a blue spectrum, such as hybrid inflation models. We obtain tight, simultaneous limits on the (constant) equation of state of dark energy and the spatial curvature of the universe: 0.14 < 1 + w < 0.12(95%CL) and 0.0179 < Ω_{ k } < 0.0081(95%CL). We provide a set of "WMAP distance priors," to test a variety of dark energy models with spatial curvature. We test a timedependent w with a present value constrained as 0.33 < 1 + w _{0} < 0.21 (95% CL). Temperature and dark matter fluctuations are found to obey the adiabatic relation to within 8.9% and 2.1% for the axiontype and curvatontype dark matter, respectively. The power spectra of TB and EB correlations constrain a parityviolating interaction, which rotates the polarization angle and converts E to B. The polarization angle could not be rotated more than 5fdg9 < ∆α < 2fdg4 (95% CL) between the decoupling and the present epoch. We find the limit on the total mass of massive neutrinos of ∑m _{ν} < 0.67 eV(95%CL), which is free from the uncertainty in the normalization of the largescale structure data. The number of relativistic degrees of freedom (dof), expressed in units of the effective number of neutrino species, is constrained as N _{eff} = 4.4 ± 1.5 (68%), consistent with the standard value of 3.04. Finally, quantitative limits on physicallymotivated primordial nonGaussianity parameters are 9 < f ^{local} _{NL} < 111 (95% CL) and 151 < f ^{equil} _{NL} < 253 (95% CL) for the local and equilateral models, respectively.
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 2009
 DOI:
 10.1088/00670049/180/2/330
 arXiv:
 arXiv:0803.0547
 Bibcode:
 2009ApJS..180..330K
 Keywords:

 cosmic microwave background;
 cosmology: observations;
 dark matter;
 early universe;
 instrumentation: detectors;
 space vehicles: instruments;
 telescopes;
 Astrophysics
 EPrint:
 52 pages, 21 figures, accepted for publication in ApJS. (v2) References added. Cosmological parameters updated with the latest union supernova compilation (Kowalski et al. arXiv:0804.4142)