Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology

A simple cosmological model with only six parameters (matter density, � mh 2 , baryon density, � bh 2 , Hubble con- stant, H0, amplitude of fluctuations,� 8, optical depth,� , 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-scalestructureobservations,andthesupernovaluminosity/distancerelationship.UsingWMAPdataonly,thebest- fit values for cosmological parameters for the power-law flatcold dark matter (� CDM) model are (� mh 2 ; � bh 2 ; h;ns;�;� 8) ¼(0:1277 þ0:0080 � 0:0079 ;0:02229 � 0:00073;0:732 þ0:031 � 0:032 ;0:958 � 0:016;0:089 � 0:030;0:761 þ0:049 � 0:048 ).The3year 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 ¼ 1; r ¼ 0). Adding additionaldatasetsimprovestheconstraintsonthesecomponentsandthespectralslope.Forpower-lawmodels,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- scalepowerthrougharunningspectralindexoralarge-scalecutoffinthepowerspectrumareabetterfittotheWMAP and small-scale CMB data than the power-lawCDM model; however, the improvement in thefit to the WMAP data is only � � 2 ¼ 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) datayieldsasignificantconstraintontheequationofstateofthedarkenergy,w ¼� 0:967 þ0:073 � 0:072 .Ifweassumew ¼� 1, then the deviations from the critical density, � K, are small: the combination of WMAP and the SNLS data implies � k ¼� 0:011 � 0:012. The combination of WMAP 3 year data plus the HST Key Project constraint on H0 implies � k ¼� 0:014 � 0:017 and � � ¼ 0:716 � 0:055. Even if we do not include the prior that the universe is flat, by com- biningWMAP,large-scalestructure,andsupernovadata,wecanstillputastrongconstraintonthedarkenergyequation of state, w ¼� 1:08 � 0:12. For a flat universe, the combination of WMAP and other astronomical data yield a con- straint on the sum of the neutrino masses, P m� <0:66 eV (95%CL). Consistent with the predictions of simple infla- tionary 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.