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 DA (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 Galaxies (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 broadband power. We test the robustness of our analysis methods on 160 LasDamas DR7 mock catalogues and find that our models are unbiased at the ~0. 2% level in measuring the BAO anisotropy. After reconstruction we measure DA (z=0. 35) =1050+/-38 Mpc and H (z=0. 35) =84. 4+/-7. 0 km/s/Mpc assuming a sound horizon of rₛ=152. 76 Mpc. Note that these measurements are correlated with a correlation coefficient of 0. 58. This represents a factor of 1. 4 improvement in the error on DA relative to the pre-reconstruction case; a factor of 1. 2 improvement is seen for H.