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We present the measurement of the two-point cross-correlation function (CCF) of 8198 Sloan Digital Sky Survey Data Release 7 quasars and 349,608 Data Release 10 CMASS galaxies from the Baryonic Oscillation Spectroscopic Survey at 0.3 < z < 0.9. The CCF can be reasonably well fit by a power-law model ξQG(r) = (r/r0)–γ on projected scales of rp = 2-25 h–1 Mpc with r0 = 6.61 ± 0.25 h–1 Mpc and γ = 1.69 ± 0.07. We estimate a quasar linear bias of bQ = 1.38 ± 0.10 at 〈 z〉 = 0.53 from the CCF measurements, which corresponds to a characteristic host halo mass of ∼4 × 1012h–1M☼, compared with a ∼1013h–1M☼ characteristic host halo mass for CMASS galaxies. Based on the clustering measurements, most quasars at are not the descendants of their higher luminosity counterparts at higher redshift, which would have evolved into more massive and more biased systems at low redshift. We divide the quasar sample in luminosity and constrain the luminosity dependence of quasar bias to be dbQ/dlog L = 0.20 ± 0.34 or 0.11 ± 0.32 (depending on different luminosity divisions) for quasar luminosities –23.5 > Mi(z = 2) > –25.5, implying a weak luminosity dependence of clustering for luminous quasars at . We compare our measurements with theoretical predictions, halo occupation distribution (HOD) models, and mock catalogs. These comparisons suggest that quasars reside in a broad range of host halos. The host halo mass distributions significantly overlap with each other for quasars at different luminosities, implying a poor correlation between halo mass and instantaneous quasar luminosity. We also find that the quasar HOD parameterization is largely degenerate such that different HODs can reproduce the CCF equally well, but with different satellite fractions and host halo mass distributions. These results highlight the limitations and ambiguities in modeling the distribution of quasars with the standard HOD approach. [ABSTRACT FROM AUTHOR]

We measure the luminosity and color dependence and the redshift evolution of galaxy clustering in the Sloan Digital Sky Survey-III Baryon Oscillation Spectroscopic Survey Ninth Data Release. We focus on the projected two-point correlation function (2PCF) of subsets of its CMASS sample, which includes about 260,000 galaxies over ∼3300 deg2 in the redshift range 0.43 < z < 0.7. To minimize the selection effect on galaxy clustering, we construct well-defined luminosity and color subsamples by carefully accounting for the CMASS galaxy selection cuts. The 2PCF of the whole CMASS sample, if approximated by a power-law, has a correlation length of r0 = 7.93 ± 0.06 h -1 Mpc and an index of γ = 1.85 ± 0.01. Clear dependences on galaxy luminosity and color are found for the projected 2PCF in all redshift bins, with more luminous and redder galaxies generally exhibiting stronger clustering and steeper 2PCF. The color dependence is also clearly seen for galaxies within the red sequence, consistent with the behavior of SDSS-II main sample galaxies at lower redshifts. At a given luminosity (k + e corrected), no significant evolution of the projected 2PCFs with redshift is detected for red sequence galaxies. We also construct galaxy samples of fixed number density at different redshifts, using redshiftdependent magnitude thresholds. The clustering of these galaxies in the CMASS redshift range is found to be consistent with that predicted by passive evolution. Our measurements of the luminosity and color dependence and redshift evolution of galaxy clustering will allow for detailed modeling of the relation between galaxies and dark matter halos and new constraints on galaxy formation and evolution. [ABSTRACT FROM AUTHOR]

We investigate the radial distribution of galaxies within their host dark matter halos as measured in the Sloan Digital Sky Survey by modeling their small-scale clustering. Specifically, we model the Jiang et al. measurements of the galaxy two-point correlation function down to very small projected separations (10 h-1 kpc ≤ r ≤ 400 h-1 kpc), in a wide range of luminosity threshold samples (absolute r-band magnitudes of -18 up to -23). We use a halo occupation distribution framework with free parameters that specify both the number and spatial distribution of galaxies within their host dark matter halos. We assume one galaxy resides in the halo center and additional galaxies are considered satellites that follow a radial density profile similar to the dark matter Navarro-Frenk-White (NFW) profile, except that the concentration and inner slope are allowed to vary. We find that in low luminosity samples (Mr < -19.5 and lower), satellite galaxies have radial profiles that are consistent with NFW. Mr < -20 and brighter satellite galaxies have radial profiles with significantly steeper inner slopes than NFW (we find inner logarithmic slopes ranging from -1.6t o -2.1, as opposed to -1 for NFW). We define a useful metric of concentration, M1/10, which is the fraction of satellite galaxies (or mass) that are enclosed within one-tenth of the virial radius of a halo. We find that M1/10 for low-luminosity satellite galaxies agrees with NFW, whereas for luminous galaxies it is 2.5-4 times higher, demonstrating that these galaxies are substantially more centrally concentrated within their dark matter halos than the dark matter itself. Our results therefore suggest that the processes that govern the spatial distribution of galaxies, once they have merged into larger halos, must be luminosity dependent, such that luminous galaxies become poor tracers of the underlying dark matter. [ABSTRACT FROM AUTHOR]

We constrain the linear and quadratic bias parameters from the configuration dependence of the three-point correlation function (3PCF) in both redshift and projected space, utilizing measurements of spectroscopic galaxies in the Sloan Digital Sky Survey Main Galaxy Sample. We show that bright galaxies (Mr < -21.5) are biased tracers of mass, measured at a significance of 4.5σ, in redshift space and 2.5σ in projected space by using a thorough error analysis in the quasi-linear regime (9-27 h-1 Mpc). Measurements on a fainter galaxy sample are consistent with an unbiased model. We demonstrate that a linear bias model appears sufficient to explain the galaxy-mass bias of our samples, although a model using both linear and quadratic terms results in a better fit. In contrast, the bias values obtained from the linear model appear in better agreement with the data by inspection of the relative bias and yield implied values of σ8 that are more consistent with current constraints. We investigate the covariance of the 3PCF, which itself is a measurement of galaxy clustering. We assess the accuracy of our error estimates by comparing results from mock galaxy catalogs to jackknife re-sampling methods. We identify significant differences in the structure of the covariance. However, the impact of these discrepancies appears to be mitigated by an eigenmode analysis that can account for the noisy, unresolved modes. Our joint analysis of both redshift space and projected measurements allows us to identify systematic effects affecting constraints from the 3PCF. [ABSTRACT FROM AUTHOR]