Forming Super-Massive Black Hole Seeds under the Influence of a Nearby Anisotropic Multi-Frequency Source

TL;DR

This study models the impact of anisotropic multi-frequency radiation from nearby galaxies on collapsing halos, identifying optimal conditions for forming massive black hole seeds in the early universe.

Contribution

It introduces a detailed radiative transfer simulation considering multi-frequency radiation and anisotropy, revealing optimal distances for black hole seed formation.

Findings

Optimal zone for black hole seed formation is between 1-4 kpc from the galaxy.

Halo near 1-2 kpc develops a large central core of 5000-10000 solar masses.

Environment supports formation of massive primordial stars leading to black holes.

Abstract

The photo-dissociation of H$_2$ by a nearby anisotropic source of radiation is seen as a critical component in creating an environment in which a direct collapse black hole may form. Employing radiative transfer we model the effect of multi-frequency (0.76 eV - 60 eV) radiation on a collapsing halo at high redshift. We vary both the shape of the spectrum which emits the radiation and the distance to the emitting galaxy. We use blackbody spectra with temperatures of $\rm{T = 10^4\ K}$ and $\rm{T = 10^5\ K}$ and a realistic stellar spectrum. We find that an optimal zone exists between 1 kpc and 4 kpc from the emitting galaxy. If the halo resides too close to the emitting galaxy the photo-ionising radiation creates a large HII region which effectively disrupts the collapsing halo, too far from the source and the radiation flux drops below the level of the expected background and the H$_2$ fraction remains too high. When the emitting galaxy is initially placed between 1 kpc and 2 kpc from the collapsing halo, with a spectral shape consistent with a star-forming high redshift galaxy, then a large central core forms. The mass of the central core is between 5000 and 10000 $\rm{M_{\odot}}$ at a temperature of approximately 1000 K. This core is however surrounded by a reservoir of hotter gas at approximately 8000 K which leads to mass inflow rates of the order of $\sim 0.1$ $\rm{M_{\odot}}$ yr$^{-1}$. This environment has the potential to form a massive primordial star which can then lead to the formation of a direct collapse black hole.