Super-Eddington accretion in high-redshift quasar hosts: black-hole driven outflows, galaxy quenching, and the nature of Little Red Dots

Abstract: The advent of the James Webb Space Telescope has revolutionised our understanding of the high-redshift Universe, detecting bright, massive galaxies up to $z\gtrsim 10$, and identifying peculiar sources called "Little Red Dots" (LRDs). The origin of both classes of objects remains uncertain but is likely linked to the formation and early growth of the first massive black holes (MBHs), which may be more easily explained by invoking phases of super-Eddington accretion. In this study, we use a state-of-the-art zoom-in cosmological simulation of a quasar host to investigate whether these objects, during their assembly, can resemble any of the peculiar sources observed with JWST. We find that the impact of MBH feedback on star formation is typically moderate, with outflows preferentially escaping perpendicular to the galactic disc. However, for approximately ten percent of the galaxy's lifetime, the system enters a distinct quenched phase, after a rapid MBH growth driven by super-Eddington accretion. This phase culminates in a powerful feedback event, during which the MBH jet and disc-driven winds interact directly with the galactic disc, carving out a central cavity. We also find that, during the history of the quasar host progenitor, the spectral properties of the system can resemble both LRDs and quenched galaxies, depending on the specific evolutionary stage considered. These findings suggest that both conditions may represent transient phases in the life cycle of high-redshift galaxies.