The role of AGN in the migration of early-type galaxies from the blue cloud to the red sequence

TL;DR

This paper explores how AGN activity influences the transformation of early-type galaxies from star-forming blue cloud to quiescent red sequence, highlighting the timing of black hole accretion and its impact on star formation.

Contribution

It provides a new evolutionary sequence model showing AGN activity occurs after star formation ceases, challenging previous assumptions about AGN's role in galaxy quenching.

Findings

Black hole accretion mainly occurs in post-starburst galaxies.

AGN activity in the green valley is too late to quench star formation.

Early-stage low-luminosity AGN may destroy molecular gas, halting star formation.

Abstract

We present a general picture of the ongoing formation and evolution of early-type galaxies via a specific evolutionary sequence starting in the blue cloud and ending in the low-mass end of the red sequence. This evolutionary sequence includes a Seyfert AGN phase in the green valley, but this phase occurs too late after the shutdown of star formation to be responsible for it. Thus, the bulk of black hole accretion in low-redshift early-type galaxies occurs in post-starburst objects, and not concurrent with star formation. On the other hand, a low-luminosity AGN phase switching on at an earlier stage when some star formation activity remains may be responsible for destroying the molecular gas reservoir fueling star formation.