The clustering and photometric properties of faint galaxies

A photometric survey of faint galaxies in three high Galactic latitude fields (each ~ 49 arcmin2) with sub-arcsecond seeing is used to study the clustering properties of the faint galaxy population. Multi-colour photometry of the galaxies has been obtained to magnitude limits of V ~ 25, R ~ 25 and I ~ 24. Two approaches are utilized to examine the clustering: close pair and angular correlation analysis. The number of close pairs of galaxies observed to faint magnitude limits, when compared to nearby samples, determines the interaction or merger rate as a function of redshift. The prevalence of mergers at intermediate redshifts is fundamental to understanding how galaxies evolve and the relative population of galaxy types. Mergers have been used to explain the excess of galaxies in faint blue counts above the numbers expected from no-evolution models. Using the deep imaging from one of the fields, a pair fraction is determined which is consistent with the galaxies in the sample being randomly distributed with no significant excess of close pairs. This is contrary to the pair fraction of 34% ± 9% found by other authors for similar magnitude limits and using an identical approach to the pair analysis. Various reasons for this discrepancy are discussed. Colours and morphologies of our close pairs are consistent with the bulk of them being random superpositions although, as indicators of interaction, these criteria are uncertain due to contamination of field galaxies and difficulty in seeing galactic structure at intermediate redshifts, respectively. This observed lack of close pairs is probably linked with the decreasing amplitude of the angular correlation function at faint limits. If our faint samples are comprised of galaxies which have a higher average redshift than brighter samples studied by other workers then either the merger rate has been overestimated or there is a change in its behaviour from what is observed at brighter magnitude limits. [More abstract follows]Science, Faculty ofPhysics and Astronomy, Department ofGraduat