The Clustering of SDSS Galaxy Groups: Mass and Color Dependence

Abstract

We use a large sample of galaxy groups selected from the SDSS data release 4 with an adaptive halo-based group finder to probe how the clustering strength of groups depends on their masses and colors. In particular, we determine the relative biases of groups of different masses, as well as that of groups with the same mass but with different colors (either that of the central galaxy, or the total color of all group members). In agreement with previous studies, we find that more massive groups are more strongly clustered, and the inferred mass dependence of the halo bias is in good agreement with predictions for the ΛCDM concordance cosmology. Regarding the color dependence, we find that groups with red centrals are more strongly clustered than groups of the same mass but with blue centrals. Similar results are obtained when the color of a group is defined to be the total color of its member galaxies. The color dependence is more prominent in less massive groups and becomes insignificant in groups with masses > ∼ 10 14 h −1 M ⊙ . These results are consistent with those obtained by Yang et al. from an analysis of the 2dFGRS, but inconsistent with those obtained by Berlind et al. , who also used an SDSS group catalogue. We construct a mock galaxy redshift survey from the large Millennium N -body simulation that is populated with galaxies according to the semi-analytical model of Croton et al. Applying our group finder to this mock survey, and analyzing the mock data in exactly the same way as the true data, we are able to accurately recover the intrinsic mass and color dependencies of the halo bias in the model. Interestingly, the semi-analytical model reveals the same color dependence of the halo bias as we find in our group catalogue. In halos with M ∼ 10 12 h −1 M ⊙ , though, the strength of the color dependence is much stronger in the model than in the data. We discuss these results in light of the assembly bias of dark matter halos and the star formation histories of galaxies. Subject headings: dark matter -large-scale structure of the universe -galaxies: halos

The effect of cosmic web filaments on the properties of groups and their central galaxies

“…However, at very low masses (M g < 12h −1 M ), central galaxies in the D3 sample also have redder colors than those in the D2 sample. The results agree with Yang et al (2006) and Wang et al (2008), where they showed that groups with the same mass are less clustered if their central galaxies are bluer. If we associate central galaxy color to age, this result agree with Lacerna et al (2014) where they find that old central galaxies have a higher clustering amplitude at scales > 1 h −1 Mpc than young central galaxies of equal host halo mass.…”

Galaxy assembly bias: a significant source of systematic error in the galaxy–halo relationship

“…Yang et al (2006) studied the cross-correlation between galaxies and galaxy groups in the Two Degree Field Galaxy Redshift Survey (2dFGRS, Colless et al 2001), and found that for groups of the same mass, the correlation strength depends on the star formation rate (SFR) of the central galaxy: at fixed mass, the clustering strength of galaxy groups decreases as the SFR of the central galaxy increases. Wang et al (2008) and Wang et al (2013) confirmed these findings using much larger data sets obtained from the SDSS, showing that the color dependence is more prominent in less massive groups, and demonstrating that these results are consistent with predictions from semi-analytical models. These studies suggest that assembly bias may be present in the observed galaxy distribution at a statistically significant level.…”

Revealing the Cosmic Web-dependent Halo Bias

“…Additional confirmed findings were made from various observations (e.g. Blanton & Berlind 2007;Swanson et al 2008;Wang et al 2008Wang et al , 2013Deason et al 2013;Lacerna et al 2014;Miyatake et al 2016). However, null detection was also reported (e.g.…”