Suzaku View of the Swift/BAT Active Galactic Nuclei. III. Application of Numerical Torus Models to Two Nearly Compton Thick AGNs (NGC 612 and NGC 3081)

TL;DR

This study applies advanced numerical torus models to Suzaku X-ray spectra of two nearly Compton-thick AGNs, revealing their torus geometries and demonstrating the effectiveness of such models in understanding AGN structures.

Contribution

The paper introduces the application of Monte Carlo-based numerical torus models to real AGN spectra, providing detailed geometric insights into the obscuring tori of NGC 612 and NGC 3081.

Findings

NGC 612 has a torus half opening-angle of 60-70 degrees and is viewed nearly edge-on.

NGC 3081 has a small opening angle of about 15 degrees and is viewed face-on.

Numerical torus models successfully explain the broad band spectra of these AGNs.

Abstract

The broad band spectra of two Swift/BAT AGNs obtained from Suzaku follow-up observations are studied: NGC 612 and NGC 3081. Fitting with standard models, we find that both sources show similar spectra characterized by a heavy absorption with $N_{\rm{H}} \simeq 10^{24} \ \rm{cm}^{-2}$, the fraction of scattered light is $f_{\rm{scat}} = 0.5-0.8%$, and the solid angle of the reflection component is $\Omega/2\pi = 0.4-1.1$. To investigate the geometry of the torus, we apply numerical spectral models utilizing Monte Carlo simulations by Ikeda et al. (2009) to the Suzaku spectra. We find our data are well explained by this torus model, which has four geometrical parameters. The fit results suggest that NGC 612 has the torus half opening-angle of $\simeq 60^{\circ}-70^{\circ}$ and is observed from a nearly edge-on angle with a small amount of scattering gas, while NGC 3081 has a very small opening angle $\simeq 15^\circ$ and is observed on a face-on geometry, more like the deeply buried "new type" AGNs found by Ueda et al. (2007). We demonstrate the potential power of direct application of such numerical simulations to the high quality broad band spectra to unveil the inner structure of AGNs.