Measuring DA and H at z=0.35 from the SDSS DR7 LRGs using baryon acoustic oscillations

We present measurements of the angular diameter distance D-A(z) and the Hubble parameter H(z) at z = 0.35 using the anisotropy of the baryon acoustic oscillation (BAO) signal measured in the galaxy clustering distribution of the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) luminous red galaxy (LRG) sample. Our work is the first to apply density-field reconstruction to an anisotropic analysis of the acoustic peak. Reconstruction partially removes the effects of non-linear evolution and redshift-space distortions in order to sharpen the acoustic signal. We present the theoretical framework behind the anisotropic BAO signal and give a detailed account of the fitting model we use to extract this signal from the data. Our method focuses only on the acoustic peak anisotropy, rather than the more model-dependent anisotropic information from the broad-band power. We test the robustness of our analysis methods on 160 Large Suite of Dark Matter Simulation DR7 mock catalogues and find that our models are unbiased at the similar to 0.2 per cent level in measuring the BAO anisotropy. After reconstruction we measure D-A(z = 0.35) = 1050 +/- 38 Mpc and H(z = 0.35) = 84.4 +/- 7.0 km s(-1) Mpc(-1) assuming a sound horizon of r(s) = 152.76 Mpc. Note that these measurements are correlated with a correlation coefficient of 0.57. This represents a factor of 1.4 improvement in the error on D-A relative to the pre-reconstruction case; a factor of 1.2 improvement is seen for H.