The dependence of clustering on galaxy properties

Abstract

We use a sample of ∼200 000 galaxies drawn from the Sloan Digital Sky Survey (SDSS) with 0.01 < z < 0.3 and −23 < M 0.1r < −16 to study how clustering depends on properties such as stellar mass (M*), colour (g−r), 4000-Å break strength (D4000), concentration index (C), and stellar surface mass density (μ*). Our measurements of wp(rp) as a function of the r-band luminosity are in excellent agreement with the previous two-degree Field Galaxy Redshift Survey and SDSS analyses. We compute wp(rp) as a function of stellar mass and we find that more-massive galaxies cluster more strongly than less-massive galaxies, with the difference increasing above the characteristic stellar mass M* of the Schechter mass function. We then divide our sample according to colour, 4000-Å break strength, concentration and surface density. As expected, galaxies with redder colours, larger 4000-Å break strengths, higher concentrations and larger surface mass densities cluster more strongly. The clustering differences are largest on small scales and for low-mass galaxies. At fixed stellar mass, the dependences of clustering on colour and 4000-Å break strength are similar. Different results are obtained when galaxies are split by concentration or surface density. The dependence of wp(rp) on g−r and D4000 extends out to physical scales that are significantly larger than those of individual dark matter haloes (>5 h−1 Mpc). This large-scale clustering dependence is not seen for the parameters C or μ*. On small scales (<1 h−1 Mpc), the amplitude of the correlation function is constant for ‘young’ galaxies with 1.1 < D4000 < 1.5 and a steeply rising function of age for ‘older’ galaxies with D4000 > 1.5. In contrast, the dependence of the amplitude of wp(rp) on concentration on scales less than 1 h−1 Mpc is strongest for disc-dominated galaxies with C < 2.6. This demonstrates that different processes are required to explain environmental trends in the structure and in the star formation history of galaxies.