Exploring Supermassive Black Hole Feedback in Novel Regimes of the IllustrisTNG Universe: Dense Environments and Early Cosmic Times

Supermassive black holes (SMBHs) and their host galaxies evolve in tandem, with active galactic nuclei (AGN) playing a critical role in regulating galaxy growth. While the impact of AGN feedback on massive, central galaxies in the local Universe is known to be important, the relative significance of SMBHs across different galaxy environments and redshifts still lacks consensus. In two complementary studies, we leverage the state-of-the-art IllustrisTNG cosmological simulations to investigate the co-evolution of SMBHs and galaxies, focusing on massive galaxies that undergo extreme transformations in dense cosmological environments, as well as those that are quenched in the high-redshift Universe. We find that z ≈ 0 satellite galaxies that are stripped of their gas during infall into galaxy groups and clusters exhibit elevated AGN fractions, indicating that extreme environments can enhance SMBH activity. Furthermore, our analysis of z ≳ 3 massive galaxies shows that AGN feedback is the primary mechanism suppressing their star formation: rapid SMBH growth and the early onset of kinetic feedback efficiently deplete cold gas reservoirs, with dense large-scale structures further amplifying the quenching process. Together, these results highlight the role of AGN feedback as a driver of galaxy evolution across a wide range of environments and cosmic times.