Cosmological constraints from the clustering of the Sloan Digital Sky Survey DR7 luminous red galaxies

Abstract

We present the power spectrum of the reconstructed halo density field derived from a sample of luminous red galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS) Seventh Data Release (DR7). The halo power spectrum has a direct connection to the underlying dark matter power for k ≤ 0.2 h Mpc −1 , well into the quasi-linear regime. This enables us to use a factor of ∼8 more modes in the cosmological analysis than an analysis with k max = 0.1 h Mpc −1 , as was adopted in the SDSS team analysis of the DR4 LRG sample. The observed halo power spectrum for 0.02 < k < 0.2 h Mpc −1 is well fitted by our model: χ 2 = 39.6 for 40 degrees of freedom for the best-fitting Λ cold dark matter (ΛCDM) model. We find Ω m h 2 ( n s /0.96) 1.2 = 0.141 +0.010 −0.012 for a power-law primordial power spectrum with spectral index n s and Ω b h 2 = 0.022 65 fixed, consistent with cosmic microwave background measurements. The halo power spectrum also constrains the ratio of the comoving sound horizon at the baryon-drag epoch to an effective distance to z = 0.35: r s / D V (0.35) = 0.1097 +0.0039 −0.0042 . Combining the halo power spectrum measurement with the Wilkinson Microwave Anisotropy Probe ( WMAP ) 5 year results, for the flat ΛCDM model we find Ω m = 0.289 ± 0.019 and H 0 = 69.4 ± 1.6 km s −1 Mpc −1 . Allowing for massive neutrinos in ΛCDM, we find eV at the 95 per cent confidence level. If we instead consider the effective number of relativistic species N eff as a free parameter, we find N eff = 4.8 +1.8 −1.7 . Combining also with the Kowalski et al. supernova sample, we find Ω tot = 1.011 ± 0.009 and w =−0.99 ± 0.11 for an open cosmology with constant dark energy equation of state w . The power spectrum and a module to calculate the likelihoods are publicly available at http://lambda.gsfc.nasa.gov/toolbox/lrgdr/ .