The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey : modelling of the luminosity and colour dependence in the Data Release 10

Abstract

We investigate the luminosity and colour dependence of clustering of CMASS galaxies in the Sloan Digital Sky Survey-III Baryon Oscillation Spectroscopic Survey Data Release 10, focusing on projected correlation functions of well-defined samples extracted from the full catalogue of ∼540 000 galaxies at z ∼ 0.5 covering about 6500 deg2. The halo occupation distribution framework is adopted to model the measurements on small and intermediate scales (from 0.02 to 60 h−1 Mpc), infer the connection of galaxies to dark matter haloes and interpret the observed trends. We find that luminous red galaxies in CMASS reside in massive haloes of mass M ∼ 1013–1014 h−1 M⊙ and more luminous galaxies are more clustered and hosted by more massive haloes. The strong small-scale clustering requires a fraction of these galaxies to be satellites in massive haloes, with the fraction at the level of 5–8 per cent and decreasing with luminosity. The characteristic mass of a halo hosting on average one satellite galaxy above a luminosity threshold is about a factor of 8.7 larger than that of a halo hosting a central galaxy above the same threshold. At a fixed luminosity, progressively redder galaxies are more strongly clustered on small scales, which can be explained by having a larger fraction of these galaxies in the form of satellites in massive haloes. Our clustering measurements on scales below 0.4 h−1 Mpc allow us to study the small-scale spatial distribution of satellites inside haloes. While the clustering of luminosity-threshold samples can be well described by a Navarro–Frenk–White profile, that of the reddest galaxies prefers a steeper or more concentrated profile. Finally, we also use galaxy samples of constant number density at different redshifts to study the evolution of luminous red galaxies, and find the clustering to be consistent with passive evolution in the redshift range of 0.5 ≲ z ≲ 0.6.