A 2.5 per cent measurement of the growth rate from small-scale redshift space clustering of SDSS-III CMASS galaxies

Abstract

We perform the first fit to the anisotropic clustering of Sloan Digital Sky Survey III CMASS data release 10 galaxies on scales of ∼0.8-32 h^-1 Mpc. A standard halo occupation distribution model evaluated near the best-fitting Planck Λ cold dark matter (ΛCDM) cosmology provides a good fit to the observed anisotropic clustering, and implies a normalization for the peculiar velocity field of M ∼ 2 × 10¹³h^-1 M_⊙ haloes of fσ₈(z = 0.57) = 0.450 ± 0.011. Since this constraint includes both quasi-linear and non-linear scales, it should severely constrain modified gravity models that enhance pairwise infall velocities on these scales. Though model dependent, our measurement represents a factor of 2.5 improvement in precision over the analysis of DR11 on large scales, fσ₈(z = 0.57) = 0.447 ± 0.028, and is the tightest single constraint on the growth rate of cosmic structure to date. Our measurement is consistent with the Planck ΛCDM prediction of 0.480 ± 0.010 at the ∼1.9σ level. Assuming a halo mass function evaluated at the best-fitting Planck cosmology, we also find that 10 per cent of CMASS galaxies are satellites in haloes of mass M ∼ 6 × 10¹³ h^-1 M_⊙. While none of our tests and model generalizations indicate systematic errors due to an insufficiently detailed model of the galaxy-halo connection, the precision of these first results warrant further investigation into the modelling uncertainties and degeneracies with cosmological parameters.