Determination of cosmological parameters from large scale structure observations

Abstract

The possibility of determining cosmological parameters on the basis of a wide set of observational data including the Abell-ACO cluster power spectrum and mass function, peculiar velocities of galaxies, the distribution of Ly-$α$ clouds and CMB temperature fluctuations is analyzed. Using a $χ^2$ minimization method, assuming $Ω_Λ+Ω_m =1$ and no contribution from gravity waves, we found that a tilted $Λ$MDM model with one sort of massive neutrinos and the parameters $n\approx 1.12$, $Ω_m\approx 0.4$ ($Ω_Λ\approx 0.6$), $Ω_{cdm}\approx 0.3$, $Ω_ν\approx 0.06$, $Ω_b\approx 0.04$ and $h\approx 0.7$ matches observational data best. $Ω_ν$ is higher for more species of massive neutrinos, $\sim 0.1$ for two and $\sim 0.13$ for three species. $Ω_m$ raises by $\sim 0.08$ and $\sim 0.15$ respectively. Varying only a subset of parameters and fixing the others shows also that the observational data set used here rules out pure CDM models with $h\ge 0.5$, scale invariant primordial power spectrum, zero cosmological constant and spatial curvature at a very high confidence level, $>99.99%$. The corresponding class of MDM models are ruled out at $\sim 95%$ C.L. It is notable also that this data set determines the amplitude of scalar fluctuations approximately at the same level as COBE four-year data. It indicates that a possible tensor component in the COBE data cannot be very substantial.