Actual mechanism of AGN feedback regulating SMBH growth

Determine the actual physical mechanism of active galactic nucleus (AGN) feedback that regulates supermassive black hole growth in high-redshift galaxies, beyond the idealized kinetic (radio-mode) and thermal (quasar-mode) implementations used in RAMSES-based cosmological simulations.

Background

The paper studies early supermassive black hole (SMBH) growth using RAMSES cosmological hydrodynamic simulations and finds a two-phase growth: an initial super-Eddington phase followed by a self-regulated, sub-Eddington phase driven by AGN feedback. Results are robust across a range of feedback parameters and supernova feedback models.

However, the simulations rely on idealized AGN feedback prescriptions (kinetic at low Eddington ratios, thermal at higher ones) and isotropic coupling, which the authors acknowledge may not capture the true physical processes. They stress that the underlying physical mechanism of AGN feedback remains uncertain, and different feedback physics could alter SMBH growth predictions and reconcile extreme objects without overproducing massive black holes.