ThreeYear Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Implications for Cosmology
Abstract
A simple cosmological model with only six parameters (matter density, Ω_{m}h^{2}, baryon density, Ω_{b}h^{2}, Hubble constant, H_{0}, amplitude of fluctuations, σ_{8}, optical depth, τ, and a slope for the scalar perturbation spectrum, n_{s}) fits not only the 3 year WMAP temperature and polarization data, but also smallscale CMB data, light element abundances, largescale structure observations, and the supernova luminosity/distance relationship. Using WMAP data only, the bestfit values for cosmological parameters for the powerlaw flat Λ cold dark matter (ΛCDM) model are (Ω_{m}h^{2},Ω_{b}h^{2},h,n_{s},τ,σ_{8})=(0.1277^{+0.0080}_{0.0079},0.02229+/0.00073,0.732^{+0.031}_{0.032},0.958+/0.016,0.089+/0.030,0.761^{+0.049}_{0.048}). The 3 year data dramatically shrink the allowed volume in this sixdimensional parameter space. Assuming that the primordial fluctuations are adiabatic with a powerlaw spectrum, the WMAP data alone require dark matter and favor a spectral index that is significantly less than the HarrisonZel'dovichPeebles scaleinvariant spectrum (n_{s}=1, r=0). Adding additional data sets improves the constraints on these components and the spectral slope. For powerlaw models, WMAP data alone puts an improved upper limit on the tensortoscalar ratio, r_{0.002}<0.65 (95% CL) and the combination of WMAP and the lensingnormalized SDSS galaxy survey implies r_{0.002}<0.30 (95% CL). Models that suppress largescale power through a running spectral index or a largescale cutoff in the power spectrum are a better fit to the WMAP and smallscale CMB data than the powerlaw ΛCDM model; however, the improvement in the fit to the WMAP data is only Δχ^{2}=3 for 1 extra degree of freedom. Models with a runningspectral index are consistent with a higher amplitude of gravity waves. In a flat universe, the combination of WMAP and the Supernova Legacy Survey (SNLS) data yields a significant constraint on the equation of state of the dark energy, w=0.967^{+0.073}_{0.072}. If we assume w=1, then the deviations from the critical density, Ω_{K}, are small: the combination of WMAP and the SNLS data implies Ω_{k}=0.011+/0.012. The combination of WMAP 3 year data plus the HST Key Project constraint on H_{0} implies Ω_{k}=0.014+/0.017 and Ω_{Λ}=0.716+/0.055. Even if we do not include the prior that the universe is flat, by combining WMAP, largescale structure, and supernova data, we can still put a strong constraint on the dark energy equation of state, w=1.08+/0.12. For a flat universe, the combination of WMAP and other astronomical data yield a constraint on the sum of the neutrino masses, Σm_{ν}<0.66 eV (95%CL). Consistent with the predictions of simple inflationary theories, we detect no significant deviations from Gaussianity in the CMB maps using Minkowski functionals, the bispectrum, trispectrum, and a new statistic designed to detect largescale anisotropies in the fluctuations.
 Publication:

The Astrophysical Journal Supplement Series
 Pub Date:
 June 2007
 DOI:
 10.1086/513700
 arXiv:
 arXiv:astroph/0603449
 Bibcode:
 2007ApJS..170..377S
 Keywords:

 Cosmology: Cosmic Microwave Background;
 Cosmology: Observations;
 Astrophysics
 EPrint:
 91 pgs, 28 figs. Accepted version of the 3year paper as posted to http://lambda.gsfc.nasa.gov/product/map/dr2/map_bibliography.cfm in January 2007