First‐Year <i>Wilkinson Microwave Anisotropy Probe</i> ( <i>WMAP</i> ) Observations: Determination of Cosmological Parameters

WMAP precision data enables accurate testing of cosmological models. We find that the emerging standard model of cosmology, a flat Λ−dominated universe seeded by a nearly scaleinvariant adiabatic Gaussian fluctuations, fits the WMAP data. With parameters fixed only by WMAP data, we can fit finer scale CMB measurements and measurements of large scale structure (galaxy surveys and the Lyman α forest). This simple model is also consistent with a host of other astronomical measurements: its inferred age of the universe is consistent with stellar ages, the baryon/photon ratio is consistent with measurements of the [D]/[H] ratio, and the inferred Hubble constant is consistent with local observations of the expansion rate. We then fit the model parameters to a combination of WMAP data with other finer scale CMB experiments (ACBAR and CBI), 2dFGRS measurements and Lyman α forest data to find the model’s best fit cosmological parameters: h = 0.71 +0.04 −0.03, Ωbh2 = 0.0224 ± 0.0009, Ωmh2 = 0.135 +0.008 −0.009, τ = 0.17 ± 0.06, ns(0.05 Mpc−1) = 0.93 ± 0.03, and σ8 = 0.84 ± 0.04. WMAP’s best determination