# Radiative effects during the assembly of direct collapse black holes

## TL;DR

This study investigates the radiative feedback effects, especially Ly{ extalpha} photon scattering, during the formation of direct collapse black holes using advanced 3D cosmological simulations with detailed radiative transfer modeling.

## Contribution

It introduces a novel post-processing radiative feedback analysis incorporating Monte Carlo Ly{ extalpha} radiative transfer in high-resolution cosmological simulations of DCBH formation.

## Key findings

- Multiple scattering of Ly{ extalpha} photons provides significant mechanical feedback.
- Gas in the vicinity can become partially ionized, affecting radiation pressure.
- Full Ly{ extalpha} radiation hydrodynamics are needed for future accurate modeling.

## Abstract

We perform a post-processing radiative feedback analysis on a 3D ab initio cosmological simulation of an atomic cooling halo under the direct collapse black hole (DCBH) scenario. We maintain the spatial resolution of the simulation by incorporating native ray-tracing on unstructured mesh data, including Monte Carlo Lyman-alpha (Ly{\alpha}) radiative transfer. DCBHs are born in gas-rich, metal-poor environments with the possibility of Compton-thick conditions, $N_H \gtrsim 10^{24} {\rm cm}^{-2}$. Therefore, the surrounding gas is capable of experiencing the full impact of the bottled-up radiation pressure. In particular, we find that multiple scattering of Ly{\alpha} photons provides an important source of mechanical feedback after the gas in the sub-parsec region becomes partially ionized, avoiding the bottleneck of destruction via the two-photon emission mechanism. We provide detailed discussion of the simulation environment, expansion of the ionization front, emission and escape of Ly{\alpha} radiation, and Compton scattering. A sink particle prescription allows us to extract approximate limits on the post-formation evolution of the radiative feedback. Fully coupled Ly{\alpha} radiation hydrodynamics will be crucial to consider in future DCBH simulations.