Galaxy Clustering in the Completed SDSS Redshift Survey: The Dependence on Color and Luminosity

Abstract

We measure the luminosity and color dependence of galaxy clustering in the largest-ever galaxy redshift survey, the main galaxy sample of the Sloan Digital Sky Survey (SDSS) Seventh Data Release (DR7). We focus on the projected correlation function w p (r p ) of volume-limited samples, extracted from the parent sample of ∼ 700, 000 galaxies over 8000 deg 2 , extending up to redshift of 0.25. We interpret our measurements using halo occupation distribution (HOD) modeling assuming a ΛCDM cosmology (inflationary cold dark matter with a cosmological constant). The amplitude of w p (r p ) grows slowly with luminosity for L < L * and increases sharply at higher luminosities, with a large-scale bias factor b(> L) × (σ 8 /0.8) = 1.06 + 0.21(L/L * ) 1.12 , where L is the sample luminosity threshold. At fixed luminosity, redder galaxies exhibit a higher amplitude and steeper correlation function, a steady trend that runs through the "blue cloud" and "green valley" and continues across the "red sequence." The cross-correlation of red and blue galaxies is close to the geometric mean of their autocorrelations, dropping slightly below at r p < 1 h −1 Mpc. The luminosity trends for the red and blue galaxy populations separately are strikingly different. Blue galaxies show a slow but steady increase of clustering strength with luminosity, with nearly constant shape of w p (r p ). The large-scale clustering of red galaxies shows little luminosity dependence until a sharp increase at L > 4L * , but the lowest luminosity red galaxies (0.04 − 0.25L * ) show very strong clustering on small scales (r p < 2 h −1 Mpc). Most of the observed trends can be naturally understood within the ΛCDM+HOD framework. The growth of w p (r p ) for higher luminosity galaxies reflects an overall shift in the mass scale of their host dark matter halos, in particular an increase in the minimum host halo mass M min . The mass at which a halo has, on average, one satellite galaxy brighter than L is M 1 ≈ 17M min (L) over most of the luminosity range, with a smaller ratio above L * . The growth and steepening of w p (r p ) for redder galaxies reflects the increasing fraction of galaxies that are satellite systems in high mass halos instead of central systems in low mass halos, a trend that is especially marked at low luminosities. Our extensive measurements, provided in tabular form, will allow detailed tests of theoretical models of galaxy formation, a firm grounding of semi-empirical models of the galaxy population, and new constraints on cosmological parameters from combining real-space galaxy clustering with mass-sensitive statistics such as redshift-space distortions, cluster mass-to-light ratios, and galaxy-galaxy lensing.

Star-forming compact groups (SFCGs): an ultraviolet search for a local sample

“…This fact is in general agreement with the weaker clustering of blue galaxies in comparison with red galaxies (e.g. Zehavi et al 2011).…”

Observational probes of cosmic acceleration

“…More massive or more luminous galaxies are more strongly clustered because they reside in more massive halos that have higher b h (M ). At low redshift, the large scale bias factor is b g ≤ 1 for galaxies below the characteristic cutoff L * of the Schechter (1976) luminosity function, but it rises sharply at higher luminosities Zehavi et al, 2005Zehavi et al, , 2011.…”

“…For a galaxy sample defined by a threshold L min in optical or near-IR luminosity (or stellar mass), theoretical models and empirical studies (too numerous to list comprehensively, but our summary here is especially influenced by Kravtsov et al 2004;Conroy et al 2006;Zehavi et al 2011) suggest the following approximate model. The minimum host halo mass is the one for which the comoving space density n(M min ) of halos above M min matches the space density n(L min ) of galaxies above the luminosity threshold.…”

Dusty star-forming galaxies at high redshift

“…These include optically-selected SDSS QSOs at 0 < z < 3 (Myers et al, 2006;Ross et al, 2009) Lyman-break galaxies (Adelberger et al, 2005), MIPS 24 µm-selected star-forming galaxies at 0 < z < 1.4 , AGES and DEEP2 red and blue galaxies at 0.25 < z < 1 from the AGES (Hickox et al, 2009;Coil et al, 2008) SDSS-selected luminous red galaxies (LRGs) at 0 < z < 0.7 (Wake et al, 2008), and optically-selected galaxy clusters at 0.1 < z < 0.3 (Estrada et al, 2009). The figure also shows the r 0 for low-redshift galaxies with r-band luminosities in the range 1.5 to 3.5 L , derived from the luminosity dependence of clustering (Zehavi et al, 2011). Dotted lines show r 0 versus redshift for dark matter haloes of different masses.…”