A simple cosmological model with only six parameters (matter density, Ωmh2, baryon density, Ωbh2, Hubble constant, H0, amplitude of fluctuations, σ8, optical depth, τ, and a slope for the scalar perturbation spectrum, ns) 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 Λ cold dark matter (ΛCDM) model are (Ωmh2,Ωbh2,h,ns,τ,σ8)=(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 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 (ns=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, r0.002<0.65 (95% CL) and the combination of WMAP and the lensing-normalized SDSS galaxy survey implies r0.002<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 ΛCDM model; however, the improvement in the fit to the WMAP data is only Δχ2=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+0.073-0.072. If we assume w=-1, then the deviations from the critical density, ΩK, are small: the combination of WMAP and the SNLS data implies Ωk=-0.011+/-0.012. The combination of WMAP 3 year data plus the HST Key Project constraint on H0 implies Ωk=-0.014+/-0.017 and ΩΛ=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, Σmν<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.
The Astrophysical Journal Supplement Series
- Pub Date:
- June 2007
- Cosmology: Cosmic Microwave Background;
- Cosmology: Observations;
- 91 pgs, 28 figs. Accepted version of the 3-year paper as posted to http://lambda.gsfc.nasa.gov/product/map/dr2/map_bibliography.cfm in January 2007