Inflow Generated X-ray Corona Around Supermassive Black Holes and Unified Model for X-ray Emission

TL;DR

This study uses 3D hydrodynamic simulations to model the inflow-generated X-ray corona around supermassive black holes, explaining AGN spectra and predicting an anti-correlation between disk luminosity and spectral hardness.

Contribution

It introduces a unified physical model linking inflow gas to X-ray corona formation and AGN spectral features, incorporating detailed radiative processes.

Findings

Coronal gas is shock heated to temperatures ≥10^8 K in the inner regions.

Simulated bremsstrahlung spectra match observed AGN and X-ray background spectra.

The model predicts an anti-correlation between accretion disk luminosity and spectral hardness.

Abstract

Three-dimensional hydrodynamic simulations, covering the spatial domain from hundreds of Schwarzschild radii to $2\ \mathrm{pc}$ around the central supermassive black hole of mass $10^8 M_\odot$, with detailed radiative cooling processes, are performed. Generically found is the existence of a significant amount of shock heated, high temperature ($\geq 10^8\ \mathrm{K}$) coronal gas in the inner ($\leq 10^4 r_\mathrm{sch}$) region. It is shown that the composite bremsstrahlung emission spectrum due to coronal gas of various temperatures are in reasonable agreement with the overall ensemble spectrum of AGNs and hard X-ray background. Taking into account inverse Compton processes, in the context of the simulation-produced coronal gas, our model can readily account for the wide variety of AGN spectral shape, which can now be understood physically. The distinguishing feature of our model is that X-ray coronal gas is, for the first time, an integral part of the inflow gas and its observable characteristics are physically coupled to the concomitant inflow gas. One natural prediction of our model is the anti-correlation between accretion disk luminosity and spectral hardness: as the luminosity of SMBH accretion disk decreases, the hard X-ray luminosity increases relative to the UV/optical luminosity.