Galaxy groups in the 2MASS Redshift Survey

TL;DR

This paper presents a new galaxy group catalog derived from the 2MASS Redshift Survey using a halo-based finder, providing reliable group identifications and halo mass estimates to study the local universe.

Contribution

The paper introduces a halo-based group finder and a GAP method for estimating halo masses, validated with mock samples, applied to 2MRS, resulting in a comprehensive galaxy group catalog.

Findings

Created a catalog of 29,904 galaxy groups from 43,246 galaxies.

Achieved 80% completeness and 65% zero contamination in groups.

Estimated halo masses with a typical uncertainty of 0.35 dex.

Abstract

A galaxy group catalog is constructed from the 2MASS Redshift Survey (2MRS) with the use of a halo-based group finder. The halo mass associated with a group is estimated using a `GAP' method based on the luminosity of the central galaxy and its gap with other member galaxies. Tests using mock samples shows that this method is reliable, particularly for poor systems containing only a few members. On average 80% of all the groups have completeness >0.8, and about 65% of the groups have zero contamination. Halo masses are estimated with a typical uncertainty $\sim 0.35\,{\rm dex}$. The application of the group finder to the 2MRS gives 29,904 groups from a total of 43,246 galaxies at $z \leq 0.08$, with 5,286 groups having two or more members. Some basic properties of this group catalog is presented, and comparisons are made with other groups catalogs in overlap regions. With a depth to $z\sim 0.08$ and uniformly covering about 91% of the whole sky, this group catalog provides a useful data base to study galaxies in the local cosmic web, and to reconstruct the mass distribution in the local Universe.