The Supernova that Destroyed a Protogalaxy: Prompt Chemical Enrichment and Supermassive Black Hole Growth

TL;DR

This paper models a supermassive Pop III star explosion in a primordial galaxy, showing how it triggers metal enrichment, starburst activity, and rapid black hole growth, potentially marking the origins of supermassive black holes.

Contribution

It presents the first detailed simulation of a supermassive Pop III star explosion in a line-cooled protogalaxy, linking supernova feedback to black hole formation in early galaxies.

Findings

Supernova expands to ~1 kpc, then collapses back, mixing metals into the galaxy.

Fuels a violent starburst and rapid black hole growth.

Remnant is a detectable synchrotron source with distinctive signatures.

Abstract

The first primitive galaxies formed from accretion and mergers by z ~ 15, and were primarily responsible for cosmological reionization and the chemical enrichment of the early cosmos. But a few of these galaxies may have formed in the presence of strong Lyman-Werner UV fluxes that sterilized them of H_2, preventing them from forming stars or expelling heavy elements into the IGM prior to assembly. At masses of 10^8 Ms and virial temperatures of 10^4 K, these halos began to rapidly cool by atomic lines, perhaps forming 10^4 - 10^6 Ms Pop III stars and, later, the seeds of supermassive black holes. We have modeled the explosion of a supermassive Pop III star in the dense core of a line-cooled protogalaxy with the ZEUS-MP code. We find that the supernova (SN) expands to a radius of ~ 1 kpc, briefly engulfing the entire galaxy, but then collapses back into the potential well of the dark matter. Fallback fully mixes the interior of the protogalaxy with metals, igniting a violent starburst and fueling the rapid growth of a massive black hole at its center. The starburst would populate the protogalaxy with stars in greater numbers and at higher metallicities than in more slowly-evolving, nearby halos. The SN remnant becomes a strong synchrotron source that can be observed with eVLA and eMERLIN and has a unique signature that easily distinguishes it from less energetic SN remnants. Such explosions, and their attendant starbursts, may well have marked the birthplaces of supermassive black holes on the sky.