Three-year Wilkinson Microwave Anisotropy Probe (WMAP) observations:: Implications for cosmology

A simple cosmological model with only six parameters ( matter density, Omega(m)h(2), baryon density, Omega(b)h(2), Hubble constant, H-0, amplitude of fluctuations, sigma(8), optical depth, tau, and a slope for the scalar perturbation spectrum, n(s)) fits not only the 3 year WMAP temperature and polarization data, but also small-scale CMB data, light element abundances, large-scale structure observations, and the supernova luminosity/distance relationship. Using WMAP data only, the best-fit values for cosmological parameters for the power-law flat Lambda cold dark matter ( Lambda CDM) model are ( Omega(m)h(2), Omega(b)h(2), h, n(s), tau, sigma(s)) = (0.1277(-0.0079)(+0.0080), 0.02229 +/- 0.00073, 0.732(-0.032)(+0.031), 0.958 +/- 0.016,0.089 +/- 0.030, 0.761(-0.048)(+0.049)). The 3 year data dramatically shrink the allowed volume in this six-dimensional parameter space. Assuming that the primordial fluctuations are adiabatic with a power-law spectrum, the WMAP data alone require dark matter and favor a spectral index that is significantly less than the Harrison- Zel'dovich-Peebles scale-invariant spectrum ( n(s) = 1, r = 0). Adding additional data sets improves the constraints on these components and the spectral slope. For power-law models, WMAP data alone puts an improved upper limit on the tensor-to-scalar ratio, r(0.002) < 0.65 ( 95% CL) and the combination of WMAP and the lensing-normalized SDSS galaxy survey implies r(0.002) < 0.30 ( 95% CL). Models that suppress large-scale power through a running spectral index or a large-scale cutoff in the power spectrum are a better fit to the WMAP and small-scale CMB data than the power-law Lambda CDM model; however, the improvement in the fit to the WMAP data is only Delta(2)(chi) = 3 for 1 extra degree of freedom. Models with a running-spectral 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(-0.072)(+0.073). If we assume w = -1, then the deviations from the critical density, Omega(K), are small: the combination of WMAP and the SNLS data implies Omega(k) = -0.011 +/- 0.012. The combination of WMAP 3 year data plus the HST Key Project constraint on H-0 implies Omega(k) = -0.014 +/- 0.017 and Omega(Lambda) = 0.716 +/- 0.055. Even if we do not include the prior that the universe is flat, by combining WMAP, large-scale 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, Sigma m(nu) < 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 large-scale anisotropies in the fluctuations.