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

Abstract

We combine the Ly-α forest power spectrum (LYA) from the Sloan Digital Sky Survey (SDSS) and high resolution spectra with cosmic microwave background (CMB) including three-year WMAP, and 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 principle component analysis for quasar continua, which improves the LYA constraints on the linear power. We find some tension between the WMAP3 and LYA power spectrum amplitudes, at the ∼2σ level, which is partially alleviated by the inclusion of other observations: we find σ 8= 0.85 ± 0.02 compared to σ 8= 0.80 ± 0.03 without LYA. For the slope, we find ns= 0.965 ± 0.012. We find no evidence for the running of the spectral index in the combined analysis, d n/dln k= −(1.5 ± 1.2) × 10−2, in agreement with inflation. The limits on the sum of neutrino masses are significantly improved:at 95% (<0.32 eV at 99.9%). This result, when combined with atmospheric and solar neutrino mixing constraints, requires that the neutrino masses cannot be degenerate,m3/m1>1.3 (95% c.l.). Assuming a thermalized fourth neutrino, we find ms<0.26 eV at 95% c.l. and such a neutrino cannot be an explanation for the LSND results. In the limits of massless neutrinos, we obtain the effective number of neutrinos Nνeff= 5.3−0.6+0.4−1.7+2.1−2.5+3.8 and Nνeff= 3.04 is allowed only at 2.4 sigma. The constraint on the dark energy equation of state is w= −1.04 ± 0.06. The constraint on curvature is Ω k= −0.003 ± 0.006. Cosmic strings limits are G μ<2.3 × 10−7 at 95% c.l. and correlated isocurvature models are also tightly constrained.