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Session 112 - Galaxy Surveys.
Oral session, Thursday, January 16
Harbour C,
A photometric survey of faint galaxies in three high Galactic latitude fields is used to study the clustering properties of the faint galaxy population, with two approaches: 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, which is fundamental for understanding galaxy evolution. Using the deep imaging from one of the fields pair fractions are determined which are consistent with the galaxies in the sample being randomly distributed with no significant excess of close pairs. This is contrary to pair fractions found by other authors for similar magnitude limits and using an identical approach to the pair analysis.
Angular correlation analysis is applied to magnitude-limited and colour-selected samples of galaxies from the three fields, for larger angular separations than those studied with close pair analysis. General agreement is obtained with other recent studies which show that the amplitude of the angular correlation function (ømega(\theta)) is smoothly decreasing as a function of the R limiting magnitude. This decline of omega(\theta) rules out the viability of merger-dominated galaxy evolution models. Using redshift distributions extrapolated to faint magnitude limits, galaxy clustering evolution models are calculated and compared to the observed I-band omega(\theta). Faint galaxies are determined to have correlation lengths and clustering evolution parameters of either r_0\sim4 h^-1 Mpc and \epsilon\sim0-1; r_0\sim5-6 h^-1 Mpc and \epsilon>1; or r_0\sim2-3 h^-1 Mpc and \epsilon\sim-1.2. The first of the three cases has the most reasonable rate of clustering evolution but distinguishing the correct r_0 for the faint galaxies is not possible with the current data. No significant variations in the clustering amplitude as a function of colour are detected, for all the colour-selected galaxy samples considered.
