EVOLUTION IN THE CLUSTERING OF GALAXIES TO R=26

We present results for the two-point angular correlation function of g alaxies, omega(theta), to a limiting magnitude of r = 26. Our catalogu e is constructed from deep imaging using the COSMIC imaging spectrogra ph 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 param etrized by a power law of the form A(omega)theta(-0.8), in agreement w ith the angular clustering statistics of shallower catalogues. The der ived amplitude, A(omega), for our catalogue is small, but non-zero. We combine this measurement with the latest statistical constraints on f aint galaxy redshifts from gravitational lensing studies, which imply that the bulk of the r less than or similar to 26 field galaxies shoul d be at redshifts z similar to 1. We show that our derived A(omega) is significantly lower than that predicted from the local bright, optica lly selected galaxy correlation function using the lensing-determined galaxy redshift distribution and modest growth of clustering. This sim plistic model does not, however, allow for different correlation lengt hs for different morphological classes. This is important as we would expect to observe a varying morphological mix as a function of apparen t magnitude in our sample. At our faintest limits we reach sufficientl y high redshifts that differential K-corrections will result in the ob served galaxy mix being dominated by star-bursting dwarfs and low-surf ace-brightness irregulars, rather than the early-type systems used to define the local bright galaxy correlation function. By adopting the c orrelation function measured locally for these low-surface-brightness galaxies and assuming modest clustering evolution, we obtain reasonabl e agreement between our model and observations. This model, therefore, supports the scenario in which the high number density and low cluste ring amplitude of faint galaxies are produced by normally clustered st ar-forming dwarf galaxies at modest redshifts.