Multi-dimensional modelling of X-ray spectra for AGN accretion-disk outflows III: application to a hydrodynamical simulation

TL;DR

This study uses multi-dimensional radiative transfer simulations on hydrodynamical models of AGN disk winds to analyze their spectral signatures, revealing complex formation processes and the significant role of scattering and reprocessing in shaping observed spectra.

Contribution

It applies detailed radiative transfer modeling to hydrodynamical simulations of AGN winds, providing new insights into spectral features and ionization processes.

Findings

Spectral signatures include narrow absorption lines, broad emission lines, and a Compton hump.

Fe Kalpha line can develop a red-skewed wing due to Compton scattering.

Scattered radiation significantly influences ionization and spectral formation in the wind.

Abstract

We perform multi-dimensional radiative transfer simulations to compute spectra for a hydrodynamical simulation of a line-driven accretion disk wind from an active galactic nucleus. The synthetic spectra confirm expectations from parameterized models that a disk wind can imprint a wide variety of spectroscopic signatures including narrow absorption lines, broad emission lines and a Compton hump. The formation of these features is complex with contributions originating from many of the different structures present in the hydrodynamical simulation. In particular, spectral features are shaped both by gas in a successfully launched outflow and in complex flows where material is lifted out of the disk plane but ultimately falls back. We also confirm that the strong Fe Kalpha line can develop a weak, red-skewed line wing as a result of Compton scattering in the outflow. In addition, we demonstrate that X-ray radiation scattered and reprocessed in the flow has a pivotal part in both the spectrum formation and determining the ionization conditions in the wind. We find that scattered radiation is rather effective in ionizing gas which is shielded from direct irradiation from the central source. This effect likely makes the successful launching of a massive disk wind somewhat more challenging and should be considered in future wind simulations.