Cosmological parameters from combining theLyman-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 highresolution spectra with cosmic microwave background (CMB) including three-year WMAP,and supernovae (SN) and galaxy clustering constraints to derive new constraints oncosmological parameters. The existing LYA power spectrum analysis is supplemented byconstraints on the mean flux decrement derived using a principle component analysis forquasar continua, which improves the LYA constraints on the linear power. We findsome tension between the WMAP3 and LYA power spectrum amplitudes, at the∼2σ level, which is partially alleviated by the inclusion of other observations: we findσ8 = 0.85 ± 0.02 compared toσ8 = 0.80 ± 0.03 without LYA. Forthe slope, we find ns = 0.965 ± 0.012. We find no evidence for the running of the spectral index in the combined analysis,dn/dlnk = −(1.5 ± 1.2) × 10−2, in agreement with inflation. The limits on the sum of neutrino masses are significantlyimproved: at 95% (<0.32 eV at 99.9%). This result, when combined with atmospheric and solar neutrinomixing constraints, requires that the neutrino masses cannot be degenerate,m3/m1>1.3 (95% c.l.). Assuming a thermalized fourth neutrino, we findms<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 neutrinosNνeff = 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 isw = −1.04 ± 0.06. The constraint oncurvature is Ωk = −0.003 ± 0.006. Cosmicstrings limits are Gμ<2.3 × 10−7 at 95% c.l. and correlated isocurvature models are also tightly constrained.