Super-Eddington accretion in high-redshift quasar hosts: Black-hole driven outflows, galaxy quenching, and the nature of little red dots

Giada Quadri, Alessandro Trinca, Alessandro Lupi, Monica Colpi, Marta Volonteri

First listed 2025-05-08 | Last updated 2025-11-07

Abstract

The advent of the James Webb Space Telescope has revolutionised our understanding of the high-redshift Universe through its detection of bright, massive galaxies up to $z\gtrsim 10$ and its identification of 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 used a state-of-the-art zoom-in cosmological simulation of a quasar host to investigate whether these objects could resemble any of the peculiar sources observed with JWST during their assembly. 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 following 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 and carve 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.

Short digest

Zoom-in cosmological simulations of a quasar host including super-Eddington accretion track how MBH feedback shapes gas, star formation, and emergent spectra. Outflows usually vent perpendicular to the disc and only moderately suppress the SFR, but after rapid super-Eddington growth the galaxy spends ≈10% of its lifetime in a distinct quenched state. This phase culminates in a powerful jet+disc-wind event that couples to the disc and excavates a central cavity. Across its history the system’s spectra can look like little red dots or quenched galaxies, implying both are transient stages in early quasar hosts.

Key figures to inspect

• Figure 1 — Use the grey-shaded super-/near-Eddington intervals to link BH-mass jumps (purple, ×10^3) with drops in H2/HI and total gas; identify when fuel depletion precedes the quenched phase.
• Figure 2 — Compare the simulated SFR track to CEERS and GLASS main-sequence fits to spot the ≈10% lifetime downturn; measure how far below the sequences the system falls during quenching.
• Figure 3 — Read the energy budget: when MBH kinetic power spikes past stellar kinetic/radiative output, flag the feedback episode that triggers quenching; cross-check its timing with Figures 1–2.
• Figure 4 — Inspect gas vs. stars maps across epochs to see disc disruption and the expanding low-density bubble centered on the MBH; assess outflow geometry (perpendicular to the disc) and the size of the excavated central cavity.