2DARK天文志

Abstract: 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 three 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 LCDM model
are (Omega_m h^2, Omega_b h^2, h, n_s, tau, sigma_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 three 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). Models
that suppress large-scale power through a running spectral index or a
large-scale cut-off in the power spectrum are a better fit to the WMAP and small
scale CMB data than the power-law LCDM model; however, the improvement in the
fit to the WMAP data is only Delta chi^2 = 3 for 1 extra degree of freedom. The
combination of WMAP and other astronomical data yields significant constraints
on the geometry of the universe, the equation of state of the dark energy, the
gravitational wave energy density, and neutrino properties. Consistent with the
predictions of simple inflationary theories, we detect no significant deviations
from Gaussianity in the CMB maps.