The anatomy of the NGC 5044 group -- II. Stellar populations and star-formation histories

TL;DR

This study investigates the stellar populations and star-formation histories of galaxies in the NGC 5044 group, revealing mass-metallicity relations, evidence of tidal disruption, and gas removal processes driven by galaxy interactions within the group environment.

Contribution

It provides detailed stellar population analysis of group galaxies, highlighting environmental effects on galaxy evolution, which has been less explored compared to clusters.

Findings

Mass-metallicity relation consistent with other groups and clusters.

Lack of low-mass galaxies near the group center suggests tidal disruption.

Gas removal in star-forming galaxies likely caused by interactions with hot intragroup medium.

Abstract

The distribution of galaxy properties in groups and clusters holds important information on galaxy evolution and growth of structure in the Universe. While clusters have received appreciable attention in this regard, the role of groups as fundamental to formation of the present day galaxy population has remained relatively unaddressed. Here we present stellar ages, metallicities and alpha-element abundances derived using Lick indices for 67 spectroscopically confirmed members of the NGC 5044 galaxy group with the aim of shedding light on galaxy evolution in the context of the group environment. We find that galaxies in the NGC 5044 group show evidence for a strong relationship between stellar mass and metallicity, consistent with their counterparts in both higher and lower mass groups and clusters. Galaxies show no clear trend of age or alpha-element abundance with mass, but these data form a tight sequence when fit simultaneously in age, metallicity and stellar mass. In the context of the group environment, our data support the tidal disruption of low-mass galaxies at small group-centric radii, as evident from an apparent lack of galaxies below ~10^9 M_sun within ~100 kpc of the brightest group galaxy. Using a joint analysis of absorption- and emission-line metallicities, we are able to show that the star-forming galaxy population in the NGC 5044 group appears to require gas removal to explain the ~1.5 dex offset between absorption- and emission-line metallicities observed in some cases. A comparison with other stellar population properties suggests that this gas removal is dominated by galaxy interactions with the hot intragroup medium.