Cosmological parameters from combining the Lyman-alpha forest with CMB, galaxy clustering and SN constraints

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  • 16 April 2006
Abstract
We combine the Ly-alpha forest power spectrum (LYA) from the Sloan Digital Sky Survey (SDSS) and high resolution spectra with the cosmic microwave background (CMB) including 3-year WMAP, supernovae (SN) and galaxy clustering constraints to derive new constraints on cosmological parameters. The existing LYA power spectrum analysis is supplemented by constraints on the mean flux decrement derived using a principal component analysis for quasar continua, which improves the LYA constraints on the linear power. The joint analysis reduces the errors on all parameters and prefers the simplest 6 parameter cosmological model. We find some tension between the WMAP3 and LYA power spectrum amplitudes, at the ~2 sigma level, which is partially alleviated by the inclusion of other observations: we find sigma_8=0.85+-0.02 compared to sigma_8=0.80+-0.03 without LYA. For the slope we find n_s=0.965+-0.012. We find no evidence for running of the spectral index, dn/dln k=-0.020+-0.012, in agreement with inflation. The limits on the sum of neutrino masses are significantly improved: sum(m_nu)<0.17 eV at 95% (1.3 (95%). Assuming a thermalized fourth neutrino we find m_s4 is excluded at 99.76%. The constraint on the dark energy equation of state is w=-1.04+-0.06. The constraint on curvature is Omega_k=-0.003+-0.006. Cosmic strings limits are G mu<2.3 10^-7 at 95% c.l.

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