EVOLUTION IN THE CLUSTERING OF GALAXIES TO R=26

We present results for the two-point angular correlation function of galaxies, omega(theta), to a limiting magnitude of r = 26. Our catalogue is constructed from deep imaging using the COSMIC imaging spectrograph on the Hale 5-m telescope. The final sample is 95 per cent complete to r = 26.0, yielding similar to 5700 galaxies over a 90.1-arcmin(2) field. Our analysis shows omega(theta) for faint galaxies can be parametrized by a power law of the form A(omega)theta(-0.8), in agreement with the angular clustering statistics of shallower catalogues. The derived amplitude, A(omega), 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 less than or similar to 26 field galaxies should be at redshifts z similar to 1. We show that our derived A(omega) 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 correlation lengths 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 dwarfs and low-surface-brightness irregulars, rather than the early-type systems used to define the local bright galaxy correlation function. By adopting the correlation function measured locally for these low-surface-brightness galaxies and assuming modest clustering evolution, we obtain reasonable agreement between our model and observations. This model, therefore, 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.