The Response of Metal Rich Gas to X-Ray Irradiation from a Massive Black Hole at High Redshift: Proof of Concept

TL;DR

This study models how X-ray radiation from a massive black hole affects surrounding gas, revealing metallicity-dependent differences in temperature, column density, and outflow dynamics in early galaxy environments.

Contribution

It introduces X-ray Dominated Region physics into simulations to explore the impact of black hole X-ray radiation on ambient gas with different metallicities.

Findings

High temperatures and column densities in solar metallicity gas due to metal opacity.

Formation of X-ray induced H II regions and gas outflows in zero metallicity environments.

Metallicity influences the timing and extent of ionization and outflow phenomena.

Abstract

Observational studies show that there is a strong link between the formation and evolution of galaxies and the growth of supermassive black holes (SMBH) at their centers. However, the underlying physics of this observed relation is poorly understood. In order to study the effects of X-ray radiation on the surroundings of the black hole, we implement X-ray Dominated Region (XDR) physics into Enzo and use the radiation transport module Moray to calculate the radiative transfer for a polychromatic spectrum. In this work, we investigate the effects of X-ray irradiation, produced by a central massive black hole (MBH) with a mass of M = 5x10^4 M_(solar), on ambient gas with solar and zero metallicity. We find that in the solar metallicity case, due to high opacity of the metals, the energy deposition rate in the central region (< 20 pc) is high and hence the temperatures in the center are on the order of 10^(5-7) K. Moreover, due to the cooling ability and high intrinsic opacity of solar metallicity gas, column densities of 10^(24) cm^(-2) are reached at a radius of 20 pc from the MBH. These column densities are about 3 orders of magnitudes higher than in the zero metallicity case. Furthermore, in the zero metallicity case an X-ray induced H II region is formed already after 5.8 Myr. This causes a significant outflow of gas (~8x10^6 M_(solar) from the central region, with the gas reaching outflow velocities up to ~100 km s^(-1). At later times, ~23 Myr after we insert the MBH, we find that the solar metallicity case also develops an X-ray induced H II region, but delayed by ~17 Myr.