AGN obscuration through dusty infrared dominated flows. II. Multidimensional, radiation-hydrodynamics modeling

TL;DR

This study models how infrared radiation pressure on dust can create thick obscuring flows around active galactic nuclei, explaining observed obscuration in luminous AGNs through multidimensional radiation-hydrodynamics simulations.

Contribution

It introduces a detailed multidimensional radiation-hydrodynamics model showing IR radiation pressure can sustain obscuring outflows in AGNs with specific luminosity and optical depth.

Findings

Infrared radiation pressure drives obscuring outflows in AGNs.

Obscuration occurs in AGNs with luminosity > 0.05 L_edd.

Outflows are supported by external UV/X-ray illumination.

Abstract

We explore a detailed model in which the active galactic nucleus (AGN) obscuration results from the extinction of AGN radiation in a global flow driven by the pressure of infrared radiation on dust grains. We assume that external illumination by UV and soft X-rays of the dusty gas located at approximately 1pc away from the supermassive black hole is followed by a conversion of such radiation into IR. Using 2.5D, time-dependent radiation hydrodynamics simulations in a flux-limited diffusion approximation we find that the external illumination can support a geometrically thick obscuration via outflows driven by infrared radiation pressure in AGN with luminosities greater than $0.05\, L_{\rm edd}$ and Compton optical depth, $\tau_{\rm T}\gtrsim 1$.