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

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,aswas 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: χ² = 39.6 for 40 degrees of freedom for the best-fitting Δ cold dark matter (ΔCDM) model. We find Ω_mh²(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_bh² = 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 ΔCDM model we find Ω_m = 0.289 ± 0.019 and H₀ = 69.4 ± 1.6 km s^-1 Mpc^-1. Allowing ∑ for massive neutrinos in ΔCDM, we find σm_ν < 0.62 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/.