Joint Estimation of Cosmological Parameters fromCosmic Microwave Background and [ITAL]IRAS[/ITAL] Data

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Abstract
Observations of large-scale structure (LSS) and of the cosmic microwave background (CMB) each place separate constraints on the values of cosmological parameters. We calculate a joint likelihood based on various CMB experiments and the IRAS 1.2 Jy galaxy redshift survey and use this to find an overall optimum with respect to the free parameters. Our formulation self-consistently takes account of the underlying mass distribution, which affects both the CMB potential fluctuations and the IRAS redshift distortion. This not only allows more accurate parameter estimation but also removes the parameter degeneracy that handicaps calculations based on either approach alone. The family of cold dark matter models analyzed corresponds to a spatially flat universe with an initially scale-invariant spectrum and a cosmological constant. Free parameters in the joint model are the mass density due to all matter (Ωm), Hubble's parameter (h=H0/100 km s-1 Mpc-1), the quadrupole normalization of the CMB power spectrum (Q) in μK, and the IRAS light-to-mass bias (bIRAS). Throughout the analysis, the baryonic density (Ωb) is required to satisfy the nucleosynthesis constraint Ωbh2=0.024. Results from the two data sets show good agreement, and the joint optimum lies at Ωm=0.39, h=0.53, Q=16.95 μK, and b=1.21. The 68% confidence intervals are 0.29<ΩmhQb8=0.67 and Γ=0.15, and the age of the universe is 16.5 Gyr.

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