Physical parameters of the torus for the type 2 Seyfert IC 5063 from mid-IR and X-ray simultaneous spectral fitting

TL;DR

This study demonstrates that simultaneous spectral fitting of X-ray and mid-infrared data can effectively constrain the physical parameters of the obscuring torus in active galactic nuclei, using IC 5063 as a case study.

Contribution

It introduces a method to jointly analyze X-ray and mid-IR spectra to determine the physical properties of the AGN torus, confirming the same structure produces emissions in both wavelengths.

Findings

The combined smooth torus models fit both spectra well.

The same torus structure explains mid-IR and X-ray emissions.

The technique effectively constrains torus parameters.

Abstract

In order to understand the diversity of classes observed in active galactic nuclei (AGN), a geometrically and optically thick torus of gas and dust is required to obscure the central engine depending on the line of sight to the observer. We perform a simultaneous fitting of X-ray and mid-infrared (mid-IR) spectra to investigate if the same structure could produce both emissions and, if this the case, to obtain better constraints for the physical parameters of the torus. In this case, we take advantage of the fact that both emissions show important signatures of obscuration. We used the nearby type-2 active nucleus IC 5063 as a test object. This object is ideal because of the wealth of archival data including some high resolution data. It also has a relatively high AGN luminosity that dominates at both X-ray and mid-IR frequencies. We use high spectral resolution NuSTAR and IRS/Spitzer spectra. The AGN dusty models used several physically motivated models. We found that the combination of the smooth torus models at mid-IR by Fritz et al. (2006) and at X-rays by Balokovi\'c et al. (2018), with the viewing and half-opening angles linked to the same value, is the best choice to fit the spectra at both wavelengths. This allows us to determine all the parameters of its torus. This result suggests that the structure producing the continuum emission at mid-IR and the reflection component at X-ray is the same. Therefore, we prove that this technique can be used to infer the physical properties of the torus, at least when AGN dust dominates the mid-IR emission and the reflection component is significant at X-rays.