Compact and isolated groups of galaxies in the local universe

Abstract

An algorithm that searches for groups of galaxies in redshift catalogues has been applied to data obtained from the Sloan Digital Sky Survey DR5, which includes over half a million galaxies. The program finds galaxy groups according to chosen isolation and compactness parameters within a certain redshift range. The results for the SDSS are then compared to those previously obtained by us for the 2dF redshift catalog. Using these results it is possible to learn about the properties of these type of groups. For instance, statistical properties of masses, sizes, velocity dispersions, as well as the population of these groups. Furthermore, due to the large number and redshift range of the galaxies involved, these properties can be studied as a function of redshift. Extrapolating this result to z=0, it might be possible to extract these properties for compact and isolated groups in the local Universe.