Evolution in the clustering of galaxies to r = 26

Abstract

We present results for the two-point angular correlation function of galaxies, ω(θ) to a limiting magnitude of r=26. our catalogue is constructed from deep imaging using the COMIC imaging spectrograph on the hale 5-m telescope. The final sample is 95 percent complete to r=26.0, yielding ~5730 galaxies over a 90.1-arcmin2 field. Our analysis shows ω(θ) for faint galaxies can be parametrized by a power law, Aωθ–0.8, in agreement with the angular clustering statistics of shallower catalogues. The derived amplitude, Aω, for our catalogue is small, but non-zero. We combine this measurement with the latest statistical constraints on faint galaxy redshifts from gravitational lensing studies, which imply that the bulk of the r ≲26 field galaxies should be at redshifts z ~ 1. We show that Our derived Aω is significantly lower than that predicted from the local bright, optically selected galaxy correlation function using the lensing-determined galaxy redshift distribution and modest growth of clustering. This simplistic model does not, however, allow for different morphological classes. This is important as we would expect to observe a varying morphological mix as a function of apparent magnitude in our sample. At our faintest limits we reach sufficiently high redshifts that differential K- corrections will result in the observed galaxy mix being dominated by star-bursting dwarf and low- surface-brightness galaxies and assuming modest clustering evolution, we obtain reasonable agreement between our model and observations. This model supports the scenario in which the high number density and low clustering amplitude of faint galaxies are produced by normally clustered star forming dwarf galaxies at modest redshifts.