Measuring the Angular Correlation Function for Faint Galaxies in High Galactic Latitude Fields

Abstract

A photometric survey of faint galaxies in three high Galactic latitude fields (each ~49 arcmin²) with subarcsecond seeing is used to study the clustering properties of the faint galaxy population. Multicolor photometry of the galaxies has been obtained to magnitude limits of V~ 25, R ~ 25, and I ~ 24. Angular correlation analysis is applied to magnitude-limited and color-selected samples of galaxies from the three fields for angular separations ranging from 10'' to 126''. General agreement is obtained with other recent studies, which show that the amplitude of the angular correlation function, ω(θ), is smoothly decreasing as a function of limiting magnitude. The observed decline of ω(θ) rules out the viability of "maximal merger" galaxy evolution models. Using redshift distributions extrapolated to faint magnitude limits, models of galaxy clustering evolution are calculated and compared to the observed I band ω(θ). Faint galaxies are determined to have correlation lengths and clustering evolution parameters of either r₀ ~ 4 h^-1 Mpc and ~ 0-1; r₀ ~ 5-6 h^-1 Mpc and > 1; or r₀ ~ 2-3 h^-1 Mpc and ~ -1.2, assuming q₀ = 0.5 and with h = H₀/100 km s^-1 Mpc^-1. The latter case is for clustering fixed in comoving coordinates and is probably unrealistic since most local galaxies are observed to be more strongly clustered. Even though the first of the three cases has the most reasonable rate of clustering evolution, distinguishing the correct r₀ for the faint galaxies is not possible with the current data. No significant variations in the clustering amplitude as a function of color are detected, for all the color-selected galaxy samples considered. The validity of this result is discussed in relation to other determinations of ω(θ) for galaxies selected by color.