Measuring the Angular Correlation Function for Faint Galaxies at High Galactic Latitudes

Extract

The angular correlation function (ω(θ)) for faint, magnitude-limited samples is an important test of large scale structure formation scenarios, as well as being a valuable probe of galaxy evolution. By measuring ω(θ) one hopes to better understand the mechanism or galaxy species responsible for the number counts excess (relative to “no-evolution” models of galaxies) typically observed at blue wavelengths. Images of three ‘blank’ fields were obtained at the prime focus of the CFHT with sub-arcsecond seeing in V, R and I, to magnitude limits of 25, 24.5 and 24, respectively. The angular correlation functions calculated for one field, NF1, in V is shown in Figure 1. Clearly the amplitude of ω(θ) is decreasing at fainter magnitude limits. Note the number of objects detected are not sufficient to accurately measure ω(θ) for an individual field, in a given colour, to significantly small angular separations. In order to do this we must combine the data from our three fields and perform a multi-field fit. A full summary of this analysis will be presented in Woods et al. (1995, in prep.) including determinations of ω(θ) using galaxy samples culled from all our fields and selected by magnitude, colour and surface brightness.