The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: measuring growth rate and geometry with anisotropic clustering

Abstract

We use the observed anisotropic clustering of galaxies in the Baryon Oscillation Spectroscopic Survey Data Release 11 CMASS sample to measure the linear growth rate of structure, the Hubble expansion rate and the comoving distance scale. Our sample covers 8498 deg2 and encloses an effective volume of 6 Gpc3 at an effective redshift of bar{z} = 0.57. We find fsigma8 = 0.441 ± 0.044, H = 93.1 ± 3.0 km s-1 Mpc-1 and DA = 1380 ± 23 Mpc when fitting the growth and expansion rate simultaneously. When we fix the background expansion to the one predicted by spatially flat Lambda cold dark matter (LambdaCDM) model in agreement with recent Planck results, we find fsigma8 = 0.447 ± 0.028 (6 per cent accuracy). While our measurements are generally consistent with the predictions of LambdaCDM and general relativity, they mildly favour models in which the strength of gravitational interactions is weaker than what is predicted by general relativity. Combining our measurements with recent cosmic microwave background data results in tight constraints on basic cosmological parameters and deviations from the standard cosmological model. Separately varying these parameters, we find w = -0.983 ± 0.075 (8 per cent accuracy) and gamma = 0.69 ± 0.11 (16 per cent accuracy) for the effective equation of state of dark energy and the growth rate index, respectively. Both constraints are in good agreement with the standard model values of w = -1 and gamma = 0.554.