The DEEP2 Galaxy Redshift Survey: Clustering of Groups and Group Galaxies atz ∼ 1

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Abstract
We study the clustering properties of groups and of galaxies in groups in the DEEP2 Galaxy Redshift Survey data set at z ~ 1 in three separate fields covering a total of 2 deg2. Four measures of two-point clustering in the DEEP2 data are presented: (1) the group correlation function for 460 groups with estimated velocity dispersions of σ ≥ 200 km s-1; (2) the galaxy correlation for the full DEEP2 galaxy sample, using a flux-limited sample of 9800 objects in the range 0.7 ≤ z ≤ 1.0; (3) the galaxy correlation for galaxies in groups or in the field; and (4) the group-galaxy cross-correlation function. Our results are compared with mock group and galaxy catalogs produced from ΛCDM simulations. Using the observed number density and clustering amplitude of the DEEP2 groups, the estimated minimum group dark matter halo mass is Mmin ~ 6 × 1012 h-1 M☉. Groups are more clustered than galaxies in the DEEP2 data, with a relative bias of b = 1.17 ± 0.04 on scales rp = 0.5-15 h-1 Mpc. The correlation function of galaxies in groups has a steeper slope (γ ~ 2.12 ± 0.06) than for the full galaxy sample (γ ~ 1.74 ± 0.03), and both samples can be fit by a power law on scales rp = 0.05-20 h-1 Mpc. We empirically measure the contribution to the projected correlation function, wp(rp), for galaxies in groups from a "one-halo" term and a "two-halo" term. The projected cross-correlation between group centers and the full galaxy sample shows that red galaxies are more centrally concentrated in groups than blue galaxies at z ~ 1. DEEP2 galaxies in groups appear to have a shallower radial distribution than that of mock galaxy catalogs made from N-body simulations, which assume a central galaxy surrounded by satellite galaxies with an NFW profile. Using simulations with different halo model parameters, we show that the clustering of galaxies in groups can be used to place tighter constraints on the halo model than can be gained from using the usual galaxy correlation function alone.