Constraining Evolution in the Halo Model Using Galaxy Redshift Surveys

We use the latest observations from the 2dF Galaxy Redshift Survey to fit the conditional luminosity function (CLF) formulation of the halo-model for galaxies at z=0. This fit is then used to test the extent of evolution in the halo occupation distribution (HOD) to z=0.8, by comparing the predicted clustering from this CLF to preliminary results from the DEEP2 Redshift Survey. We show that the current observations from the DEEP2 Redshift Survey are remarkably consistent with no evolution in the CLF from z=0 to z=0.8. This result is surprising, in that it suggests that there has been very little change in the way galaxies occupy their host dark matter halos over half the age of the Universe. We discuss in detail the observational constraints we have adopted and also the various different selection effects in each survey and how these impact on the galaxy populations encountered in each survey.
11 pages, 5 figures. Minor modifications to match version accepted by ApJ