The Richness-Shape Relation of the 2dFGRS Groups

Abstract

We estimate the group shape of the recently compiled Pecolation-Inferred Galaxy Group (2PIGG) catalogue. Using a set of integral equations we invert the projected distribution of group axial ratios and recover the corresponding intrinsic distribution under the assumption that groups are pure spheroids. In agreement with the analysis of the UZC-SSRS2 group sample (Plionis, Basilakos & Tovmassian 2004) we find that groups are extremely elongated prolate-like systems. We also find an interesting trend between shape and group richness with poorer groups being significantly flatter than richer ones.

4 pages, 5 figures, submitted to Astronomy and Astrophysics (A&A)