The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: measuring H(z) and DA(z) at z=0.57 with clustering wedges

We analyse the 2D correlation function of the Sloan Digital Sky Survey-III Baryon Oscillation Spectroscopic Survey (BOSS) CMASS sample of massive galaxies of the ninth data release to measure cosmic expansion H and the angular diameter distance D-A at a mean redshift of < z > = 0.57. We apply, for the first time, a new correlation function technique called clustering wedges. xi(Delta mu) (s). Using a physically motivated model, the anisotropic baryonic acoustic feature in the galaxy sample is detected at a significance level of 4.7 sigma compared to a featureless model. The baryonic acoustic feature is used to obtain model-independent constraints cz/H/r(s) = 12.28 +/- 0.82 (6.7 percent accuracy) and D-A/r(s) = 9.05 +/- 0.27 (3.0 per cent) with a correlation coefficient of -0.5, where r(s) is the sound horizon scale at the end of the baryonic drag era. We conduct thorough tests on the data and 600 simulated realizations, finding robustness of the results regardless of the details of the analysis method. Combining this with r(s) constraints from the cosmic microwave background, we obtain H(0.57) = 90.8 +/- 6.2 km s(-1) Mpc(-1) and D-A(0.57) = 1386 +/- 45 Mpc. We use simulations to forecast results of the final BOSS CMASS data set. We apply the reconstruction technique on the simulations demonstrating that the sharpening of the anisotropic baryonic acoustic feature should improve the detection as well as tighten constraints of H and D-A by similar to 30 per cent on average.