A possible pathway to UHZ1-type systems at z~10 by heterogeneous mass primordial black holes as dark matter

TL;DR

This paper proposes a mechanism involving heterogeneous primordial black holes as dark matter to explain the formation of UHZ1-like systems at high redshift, supported by detailed modeling of early halo collapse and PBH dynamics.

Contribution

It introduces a novel formation pathway for early massive systems via PBH-induced small-scale power enhancement and dynamical evolution, aligning with recent JWST observations.

Findings

PBHs can produce early halo collapse with appropriate mass functions.

Dynamical friction causes massive PBHs to centralize in halos.

The mechanism explains properties of UHZ1 and similar high-redshift systems.

Abstract

Recent space-based observations discovered several unusual objects, exhibiting similar properties, at redshifts $z\gtrsim 10$. Among them is the UHZ1 system at $z=10.1$, containing $\sim 10^8M_\odot$ in stars, with a similarly massive central black hole of $\sim 10^{7-8}M_\odot$. Here we propose a possible mechanism for forming such systems which hinges on the presence of primordial black holes (PBHs) covering a range of masses while contributing a significant fraction of the dark matter (DM). We evaluate the accurate expression for the small-scale power responsible for the collapse of the first halos in the presence of the PBH population. The extra power in the matter density field, produced by the granulation term, will cause an earlier collapse of DM halos, populated by PBHs of different masses. In these collapsed and virialized systems the PBHs will undergo 2-body relaxation, driving the more massive PBHs to the halo center under dynamical friction. We quantify this evolution for a distribution of PBH orbital parameters and halo properties. The analysis shows that PBHs can have appropriate mass functions capable of producing systems with parameters similar to what is observed for UHZ1. We suggest that the proposed mechanism could account for a subset of other systems newly discovered with the JWST at high redshifts, including the Little Red Dots.