AGN feedback drives the colour evolution of local galaxies

TL;DR

This study demonstrates that powerful AGN feedback, especially from Fanaroff-Riley type II radio sources, significantly influences the colour and star formation activity of nearby galaxies in local groups and clusters.

Contribution

It provides observational evidence linking FR-II radio sources to galaxy colour changes and highlights the lasting impact of AGN feedback on galaxy evolution in the local universe.

Findings

Galaxies near FR-II sources are significantly redder.

FR-II sources can truncate star formation via bow shocks.

AGN feedback effects are detectable even in clusters without current radio emission.

Abstract

We investigate the effects of AGN feedback on the colour evolution of galaxies found in local (z<0.2) groups and clusters. Galaxies located within the lobes of powerful Fanaroff-Riley type II (edge-brightened) sources show much redder colours than neighbouring galaxies that are not spatially coincident with the radio source. By contrast, no similar effect is seen near Fanaroff-Riley type I (core-dominated) radio sources. We show that these colours are consistent with FR-IIs truncating star formation as the expanding bow shock overruns a galaxy. We examine a sample of clusters with no detectable radio emission and show that galaxy colours in these clusters carry an imprint of past AGN feedback. AGN activity in the low-redshift Universe is predominantly driven by low-luminosity radio sources with short duty cycles. Our results show that, despite their rarity, feedback from powerful radio sources is an important driver of galaxy evolution even in the local volume.