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

Abstract

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 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
D_A(z=0.35)=1050+/-38 Mpc and H(z=0.35)=84.4+/-7.0 km/s/Mpc assuming a sound
horizon of r_s=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 D_A relative to the pre-reconstruction case; a factor of 1.2
improvement is seen for H.