Evolution of galaxies in groups in the Coma Supercluster

TL;DR

This study investigates how different environmental factors within the Coma Supercluster influence galaxy evolution, highlighting the complex interplay between mass, local overdensities, and filamentary structures in star formation activity.

Contribution

The paper introduces a new method for characterizing local environments using kernel density estimation and provides insights into the environmental effects on galaxy evolution within the supercluster.

Findings

Environmental effects are complex and depend on multiple scales.

Pre-processing influences star formation enhancement.

The Abell 1367 region is actively assembling, increasing star formation.

Abstract

We take a close look at the galaxies in the Coma Supercluster and assess the role of the environment (in the form of cluster, group and supercluster filament) in their evolution, in particular examining the role of groups. We characterise the groups according to intrinsic properties such as richness and halo mass, as well as their position in the supercluster and proximity to the two rich clusters, Abell 1656 (Coma) and Abell 1367. We devise a new way of characterising the local environment using a kernel density estimator. We find that apart from the dominant effects of the galaxy mass, the effect of the environment on galaxies is a complex combination of the overdensities on various scales, which is characterised in terms of membership of groups, and also of the position of the galaxy on filaments and their proximity to the infall regions of clusters. Whether the gas can be turned into stars depends upon the level of pre-processing, which plays a role in how star formation is enhanced in a given environment. Our results are consistent with gas accreted in the cold mode from the filaments, being made available to enhance star formation. Finally, we show that the Abell~1367 end of the supercluster is in the process of assembly at present, leading to heightened star formation activity, in contrast with the Coma-end of the filament system.