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 kmax= 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: χ²= 39.6 for 40 degrees of freedom for the best-fitting Λ cold dark matter (ΛCDM) model. We find Ω_mh²(n_s/0.96)^1.2= 0.141^+0.101_-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 ΛCDM 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 ΛCDM, we find Σm_v <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/.