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[greater than or equal to] 0.2 h Mpc[superscript −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[subscript max]= 0.1 h Mpc[superscript −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[superscript 2]= 39.6 for 40 degrees of freedom for the best-fitting Λ cold dark matter (ΛCDM) model. We find Omega[subscript m]h2(n[subscript s]/0.96)[superscript 1.2]= 0.141+[superscript 0.010][subscript −0.012] for a power-law primordial power spectrum with spectral index n[subscript s] and Omega[subscript b]h[superscript 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[subscript s]/D[subscript V](0.35) = 0.1097[superscript +0.0039][subscript −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 Omega[subscript m]= 0.289 ± 0.019 and H[subscript 0]= 69.4 ± 1.6 km s−1 Mpc−1. Allowing for massive neutrinos in ΛCDM, we find ∑m[subscript v] <0.62 eV at the 95 per cent confidence level. If we instead consider the effective number of relativistic species N[subscript eff] as a free parameter, we find N[subscript eff]= 4.8[superscript +1.8][subscript −1.7]. Combining also with the Kowalski et al. supernova sample, we find Omega[subscript 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/.