Predicting the number density of heavy seed massive black holes due to an intense Lyman-Werner field

TL;DR

This study models the formation of massive black holes via the Lyman-Werner channel, using simulations and comparisons to other models, to assess their abundance at high redshift and compatibility with observations.

Contribution

It enhances the Lyman-Werner channel model with simulation data and compares its predictions to other models for high-redshift black hole formation.

Findings

Peak number density of ~10^{-4} cMpc^{-3} at z~10

LW-only channel likely insufficient to explain observed high-z AGN

Other models better match recent JWST observations

Abstract

The recent detections of a large number of candidate active galactic nuclei at high redshift (i.e. $z \gtrsim 4$) has increased speculation that heavy seed massive black hole formation may be a required pathway. Here we re-implement the so-called Lyman-Werner (LW) channel model of Dijkstra et al. (2014) to calculate the expected number density of massive black holes formed through this channel. We further enhance this model by extracting information relevant to the model from the $\texttt{Renaissance}$ simulation suite. $\texttt{Renaissance}$ is a high-resolution suite of simulations ideally positioned to probe the high-$z$ Universe. Finally, we compare the LW-only channel against other models in the literature. We find that the LW-only channel results in a peak number density of massive black holes of approximately $\rm{10^{-4} \ cMpc^{-3}}$ at $z \sim 10$. Given the growth requirements and the duty cycle of active galactic nuclei, this means that the LW-only is likely incompatible with recent JWST measurements and can, at most, be responsible for only a small subset of high-$z$ active galactic nuclei. Other models from the literature (e.g. rapid assembly; relative velocities between baryons and dark matter) seem therefore better positioned, at present, to explain the high frequency of massive black holes at high $z$.