Primordial Black Holes as Seeds for Extremely Overmassive AGN Observed by JWST

Abstract

The James Webb Space Telescope (JWST) has recently identified Abell 2744-QSO1 as a compact, metal-poor, black hole (BH) dominated galaxy at $z\simeq 7$. This system exhibits an extreme black-hole-to-stellar mass ratio and unusually low metallicity, posing significant challenges to BH seeding models. Motivated by these discoveries, we perform high-resolution cosmological simulations with a massive primordial black hole (PBH; $M_{\mathrm{BH}}=5\times 10^7{M}_{\odot }$) seed, incorporating for the first time a fully coupled treatment of PBH accretion, BH feedback, and Population~III/II star formation and stellar feedback. Although PBHs accelerate structure formation through the seed effect, the associated strong thermal feedback from the accretion delays the onset of star formation to $z\lesssim 10$, producing short, bursty episodes throughout the subsequent evolution. PBH-driven outflows expel enriched gas from the nucleus, while sustained inflows from the intergalactic medium continuously replenish pristine material. This feedback-regulated cycle naturally yields low accretion rates (${\dot{m}}_{\mathrm{BH}}/{\dot{m}}_{\mathrm{edd}}\sim 1-10\%$), subsolar metallicities ($Z/Z_{\odot }\lesssim 10^{-2}$) and extreme $M_{\mathrm{BH}}/M_{\star }$ ratios during both the initial star-forming phase and the subsequent quenching phases, in excellent agreement with JWST observations. Our results demonstrate that massive PBHs offer a viable pathway for forming the most extreme high-redshift systems, providing a physically motivated explanation for the extraordinary properties of Abell 2744-QSO1, as a sub-class of the broader population of JWST-discovered "little red dots".

12 pages, 3 figures, Accepted by ApJL

Cited by in corpus (4)

• Primordial Black-Hole-Based Pathways to Little Red Dots
• The Cliff: A Metal-Poor Little Red Dot Hosting an Overmassive Black Hole at $z=3.55$
• Observational Manifestations of Primordial Objects in the Early Universe Through the Hydrogen Subordinate Lines
• Smoluchowski Coagulation Equation and the Evolution of Primordial Black Hole Clusters