The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: the low-redshift sample

Abstract

We report on the small-scale (0.5 < r < 40 h⁻¹ Mpc) clustering of 78 895 massive (M_* ∼ 10^11.3 M_⊙) galaxies at 0.2 < z < 0.4 from the first two years of data from the Baryon Oscillation Spectroscopic Survey (BOSS), to be released as part of Sloan Digital Sky Survey (SDSS) Data Release 9 (DR9). We describe the sample selection, basic properties of the galaxies and caveats for working with the data. We calculate the real- and redshift-space two-point correlation functions of these galaxies, fit these measurements using halo occupation distribution (HOD) modelling within dark matter cosmological simulations, and estimate the errors using mock catalogues. These galaxies lie in massive haloes, with a mean halo mass of 5.2 × 10¹³ h⁻¹ M_⊙, a large-scale bias of ∼2.0 and a satellite fraction of 12 ± 2 per cent. Thus, these galaxies occupy haloes with average masses in between those of the higher redshift BOSS CMASS sample and the original SDSS I/II luminous red galaxy sample.