Galaxy Groups: A 2MASS Catalog

TL;DR

This paper presents a comprehensive galaxy group catalog derived from the 2MASS Redshift Survey, analyzing group properties, mass functions, and the matter density in the local universe.

Contribution

It introduces a new galaxy group catalog based on 2MASS data, with mass estimates and statistical analysis of group properties and distribution.

Findings

Identified 13,607 galaxy groups within the velocity range 3,000-10,000 km/s.

The group mass function fits the Sheth-Tormen model above 6/h x 10^12 Msun.

The total collapsed matter density is estimated at Omega_collapsed = 0.16.

Abstract

A galaxy group catalog is built from the sample of the 2MASS Redshift Survey almost complete to Ks=11.75 over 91% of the sky. Constraints in the construction of the groups were provided by scaling relations determined by close examination of well defined groups with masses between 10^11 and 10^15 Msun. Group masses inferred from Ks luminosities are statistically in agreement with masses calculated from application of the virial theorem. While groups have been identified over the full redshift range of the sample, the properties of the nearest and farthest groups are uncertain and subsequent analysis has only considered groups with velocities between 3,000 and 10,000 km/s. The 24,044 galaxies in this range are identified with 13,607 entities, 3,461 of them with two or more members. A group mass function is constructed. The Sheth-Tormen formalism provides a good fit to the shape of the mass function for group masses above 6/h x 10^12 Msun but the count normalization is poor. Summing all the mass associated with the galaxy groups between 3,000 and 10,000 km/s gives a density of collapsed matter as a fraction of the critical density of Omega_collapsed = 0.16.