paper

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

arXiv:astro-ph/0604335 · doi:10.1088/1475-7516/2006/10/014

Abstract

We combine the Ly-alpha forest power spectrum (LYA) from the Sloan Digital Sky Survey (SDSS) and high resolution spectra with cosmic microwave background (CMB) including 3-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 ~2 sigma level, which is partially alleviated by the inclusion of other observations: we find σ_8=0.85\pm 0.02 compared to sigma_8=0.80 \pm 0.03 without LYA. For the slope we find ns=0.965\pm0.012. We find no evidence for the running of the spectral index in the combined analysis, dn/dln k=-(1.5\pm 1.2) x 10^{-2}, in agreement with inflation. The limits on the sum of neutrino masses are significantly improved: $\sum m_ν<0.17\eV$ at 95% (<0.32eV at 99.9%). This result, when combined with atmospheric and solar neutrino mixing constraints, requires that the neutrino masses cannot be degenerate, m_3/m_1>1.3 (95% c.l.). Assuming a thermalized fourth neutrino we find m_s<0.26\eV at 95% c.l. and such neutrino cannot be an explanation for the LSND results. In the limits of massless neutrinos we obtain the effective number of neutrinos N_ν^{\rm eff}=5.3^{+0.4}_{-0.6}{}^{+2.1}_{-1.7}{}^{+3.8}_{-2.5} and N_ν^{\rm eff}=3.04 is allowed only at 2.4-sigma. The constraint on the dark energy equation of state is w=-1.04\pm 0.06. The constraint on curvature is Omega_k=-0.003\pm 0.006. Cosmic strings limits are Gμ<2.3 x 10^{-7} at 95% c.l. and correlated isocurvature models are also tightly constrained.

11 pages, 3 figures; v4: matches published version; v3: A numerical error found and corrected, significantly affects constraints on number of neutrino families and sterile neutrino mass, other constraints unaffected

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