Quenching of Massive Disk Galaxies in the IllustrisTNG Simulation

TL;DR

This study uses the IllustrisTNG-300 simulation to show that kinetic AGN feedback from supermassive black holes is the main mechanism quenching massive disk galaxies, which form early, retain their disk structure, and have minimal major mergers.

Contribution

It identifies kinetic AGN feedback as the key quenching process for massive, bulge-less disk galaxies in low-density environments, based on detailed simulation analysis.

Findings

Quenched disk galaxies contain less gas and larger SMBHs than star-forming ones.

They formed early and preserved disk morphology over cosmological timescales.

Kinetic AGN feedback effectively ejects gas, leading to quenching.

Abstract

A rare population of massive disk galaxies have been found to invade the red sequence dominated by early-type galaxies. These red/quenched massive disk galaxies have recently gained great interest into their formation and origins. The usually proposed quenching mechanisms, such as bar quenching and environment quenching, seem not suitable for those bulge-less quenched disks in low-density environment. In this paper, we use the IllustrisTNG-300 simulation to investigate the formation of massive quenched central disk galaxies. It is found that these galaxies contain less gas and harbor giant supermassive black holes(SMBHs) (above $ 10^{8}M_{\odot}$) than their star forming counterparts. By tracing their formation history, we found that quenched disk galaxies formed early and preserved disk morphology for cosmological time scales. They have experienced less than one major merger on average and it is mainly mini-mergers (mass ratio $<$1/10) that contribute to the growth of their SMBHs. In the Illustris-TNG simulation the black hole feedback mode switches from thermal to kinetic feedback when the black hole mass is more massive than $\sim 10^{8}M_{\odot}$, which is more efficient to eject gas outside of the galaxy and to suppress further cooling of hot gaseous halo. We conclude that kinetic AGN feedback in massive red/quenched disk galaxy is the dominant quenching mechanism.