Triggering of merger-induced starbursts by the tidal field of galaxy groups and clusters

TL;DR

This study uses N-body simulations to show that the tidal field of galaxy groups and clusters can trigger enhanced star formation during mergers, especially at high redshift, reversing the typical star formation-density relation.

Contribution

It demonstrates that the large-scale tidal field of galaxy groups and clusters can significantly boost merger-induced starbursts, a phenomenon not accounted for in previous models.

Findings

Merger-driven star formation is more active near galaxy groups and clusters.

The tidal field enhances star formation activity during mergers at high redshift.

This effect may explain the reversal of the star formation-density relation at z~1.

Abstract

Star formation in galaxies is for a part driven by galaxy mergers. At low redshift, star formation activity is low in high-density environments like groups and clusters, and the star formation activity of galaxies increases with their isolation. This star formation-density relation is observed to be reversed at z~1, which is not explained by theoretical models so far. We study the influence of the tidal field of a galaxy group or cluster on the star formation activity of merging galaxies, using N-body simulations including gas dynamics and star formation. We find that the merger-driven star formation is significantly more active in the vicinity of such cosmological structures compared to mergers in the field. The large-scale tidal field can thus enhance the activity of galaxies in dense cosmic structures, and should be particularly efficient at high redshift before quenching processes take effect in the densest regions.