The interconnection between galaxy mergers, AGN activity, and rapid quenching of star formation in simulated post-merger galaxies

We investigate the role of galaxy mergers on supermassive black hole (SMBH) accretion and star formation quenching in three state-of-the-art cosmological simulations with contrasting physics models: EAGLE, Illustris IllustrisTNG. find that recently coalesced 'post-mergers' all have elevated SMBH rates by factors ~2-5. However, rapid (within 500 Myr coalescence) is rare, incidence 0.4% Illustris, 4.5% EAGLE 10% The rarity post-mergers results from substantial gas reservoirs remain intact after merger. do successfully quench tend to be those had both low pre-merger fractions as well experience largest losses. Although quenched fraction still compared a control sample non-mergers two IllustrisTNG 11 EAGLE. Conversely, rarer than their control. Recent observational Ellison et al. found at least 30 times more common post-mergers, significantly higher excess any simulations. Our results, therefore, indicate whilst merger-induced widespread prediction simulations, its link depends sensitively models, none subgrid models studied here can fully capture connection between seen observations.