Galaxy Groups in the Third Data Release of the Sloan Digital Sky Survey

Abstract

We present a new sample of galaxy groups identified in the Sloan Digital Sky Survey Data Release 3. Following previous works, we use the well-tested friends-of-friends algorithm developed by Huchra and Geller, which takes into account the number density variation due to the apparent magnitude limit of the galaxy catalog. To improve the identification, we implement a procedure to avoid the artificial merging of small systems in high-density regions and then apply an iterative method to recompute the group centers position. As a result, we obtain a new catalog with 10,864 galaxy groups with at least four members. The final group sample has a mean redshift of 0.1 and a median velocity dispersion of 230 km s 1 .