GALAXY CLUSTERING IN THE COMPLETED SDSS REDSHIFT SURVEY: THE DEPENDENCE ON COLOR AND LUMINOSITY

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 Seventh Data Release. We focus on the projected correlation function w(p)(r(p)) of volume-limited samples, extracted from the parent sample of similar to 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 Lambda CDM 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)x(sigma(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 > 4 L-*, but the lowest luminosity red galaxies (0.04-0.25 L-*) show very strong clustering on small scales (r(p) < 2 h(-1) Mpc). Most of the observed trends can be naturally understood within the Lambda CDM+ 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 approximate to 17 M-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 semiempirical 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.