The Biggest Explosions in the Universe. II

TL;DR

This paper models energetic supernova explosions in early, dense protogalaxies, showing how fallback and turbulence promote black hole growth and produce observable signatures that could identify supermassive black hole origins.

Contribution

It introduces detailed simulations of supernova explosions in dense, line-cooled protogalaxies, revealing fallback-driven turbulence and metal distribution effects.

Findings

Supernova explosions in dense protogalaxies cause fallback and turbulence.

Metal distribution within halos is enhanced by fallback-driven mixing.

Starburst and X-ray emissions can identify early black hole formation sites.

Abstract

One of the leading contenders for the origin of supermassive black holes at $z \gtrsim$ 7 is catastrophic baryon collapse in atomically-cooled halos at $z \sim$ 15. In this scenario, a few protogalaxies form in the presence of strong Lyman-Werner UV backgrounds that quench H$_2$ formation in their constituent halos, preventing them from forming stars or blowing heavy elements into the intergalactic medium prior to formation. At masses of 10$^ 8$ \Ms\ and virial temperatures of 10$^4$ K, gas in these halos rapidly cools by H lines, in some cases forming 10$^4$ - 10$^6$ \Ms\ Pop III stars and, a short time later, the seeds of supermassive black holes. Instead of collapsing directly to black holes some of these stars died in the most energetic thermonuclear explosions in the universe. We have modeled the explosions of such stars in the dense cores of line-cooled protogalaxies in the presence of cosmological flows. In stark contrast to the explosions in diffuse regions in previous simulations, these SNe briefly engulf the protogalaxy but then collapse back into its dark matter potential. Fallback drives turbulence that efficiently distributes metals throughout the interior of the halo and fuels the rapid growth of nascent black holes at its center. The accompanying starburst and x-ray emission from these line-cooled galaxies easily distinguish them from more slowly evolving neighbors and might reveal the birthplaces of supermassive black holes on the sky.