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

Observational studies show that there is a strong link between the formation and evolution of galaxies and the growth of their supermassive black holes. However, the underlying physics behind this observed relation is poorly understood. In order to study the effects of X-ray radiation on black hole surroundings, we implement X-ray-dominated region 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 = 5 × 10⁴ M _⊙, on ambient gas with solar and zero metallicity. We find that in the solar metallicity case, the energy deposition rate in the central region (<=20 pc) is high due to the high opacity of the metals. Hence, the central temperatures are on the order of 10⁵-10⁷ K. Moreover, due to the cooling ability and high intrinsic opacity of solar metallicity gas, column densities of 10²⁴ cm^-2 are reached at a radius of 20 pc from the MBH. These column densities are about three orders of magnitudes higher than in the zero metallicity case. Furthermore, in the zero metallicity case, an X-ray-induced H II region is already formed after 5.8 Myr. This causes a significant outflow of gas (~8 × 10⁶ M _⊙) from the central region; the gas reaches 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 it is delayed by ~17 Myr compared to the zero metallicity case.