Physically motivated X-ray obscurer models

TL;DR

This study compares physically motivated models of AGN obscurers using X-ray reflection spectroscopy, finding that current observations can distinguish between different geometries and favoring a warped disk model for the Circinus Galaxy.

Contribution

Introduces new spectral models for two geometries of AGN obscurers and demonstrates their potential to differentiate these models with X-ray data.

Findings

Current X-ray spectra can distinguish between different obscurer geometries.

The warped disk model fits the Circinus Galaxy data better than the radiative fountain.

A significant population of heavily Compton-thick AGN may be hidden in local galaxies.

Abstract

The nuclear obscurer of Active Galactic Nuclei (AGN) is poorly understood in terms of its origin, geometry and dynamics. We investigate whether physically motivated geometries emerging from hydro-radiative simulations can be differentiated with X-ray reflection spectroscopy. For two new geometries, the radiative fountain model of Wada (2012) and a warped disk, we release spectral models produced with the ray tracing code XARS. We contrast these models with spectra of three nearby AGN taken by NuSTAR and Swift/BAT. Along heavily obscured sight-lines, the models present different 4-20keV continuum spectra. These can be differentiated by current observations. Spectral fits of the Circinus Galaxy favor the warped disk model over the radiative fountain, and clumpy or smooth torus models. The necessary reflector (NH>10^25/cm^2) suggests a hidden population of heavily Compton-thick AGN amongst local galaxies. X-ray reflection spectroscopy is a promising pathway to understand the nuclear obscurer in AGN.