The redshift-space two-point correlation function of galaxy groups in the CfA2 and SSRS2 surveys

We measure the two-point redshift-space correlation function of loose group s of galaxies, xi(GG)(s), for the combined CfA2 and SSRS2 surveys. Our comb ined group catalog constitutes the largest homogeneous sample available (88 5 groups). We compare xi(GG)(s) with the correlation function of galaxies, xi(gg) (s), in the same volume. We find that groups are significantly more clustered than galaxies: (xi(GG) / xi(gg) ) =1.64+/-0.16 A similar result h olds when we analyze a volume-limited sample (distance limit 78 h(-1) Mpc) of 139 groups. For these groups, with median velocity dispersion sigma(v) s imilar to 200km s(-1) and mean group separation d similar to 16 h(-1) Mpc, we find that the correlation length is s(0) = 8 +/- 1 h(-1) Mpc, which is s ignificantly smaller than that found for rich clusters. We conclude that cl ustering properties of loose groups of galaxies are intermediate between ga laxies and rich clusters. Moreover, we find evidence that group clustering depends on physical properties of groups: correlation strengthens for incre asing sigma(v).