Suzaku Observations of Heavily Obscured (Compton-thick) Active Galactic Nuclei selected by Swift/BAT Hard X-ray Survey

TL;DR

This study analyzes the X-ray spectra of 12 heavily obscured active galactic nuclei using Suzaku and Swift data, revealing insights into their intrinsic luminosity, torus structure, and relation to less obscured AGNs.

Contribution

First uniform broadband spectral analysis of 12 Compton-thick AGNs with Suzaku, comparing models and revealing properties of their obscuring tori and luminosity estimates.

Findings

Unabsorbed reflection components indicate clumpy tori.

Most CTAGNs have small scattering fractions, suggesting they are buried AGNs.

Properties of CTAGNs extend smoothly from less obscured AGNs without fundamental differences.

Abstract

We present a uniform broadband X-ray (0.5-100.0 keV) spectral analysis of 12 Swift/Burst Alert Telescope (BAT) selected Compton-thick ($\log N_{\mathrm{H}}/\mathrm{cm}^{-2} \geq 24$) Active Galactic Nuclei (CTAGNs) observed with Suzaku. The Suzaku data of 3 objects are published here for the first time. We fit the Suzaku and Swift spectra with models utilizing an analytic reflection code and those utilizing the Monte Carlo based model from an AGN torus by Ikeda et al. 2009. The main results are as follows. (1) The estimated intrinsic luminosity of a CTAGN strongly depends on the model; applying Compton scattering to the transmitted component in an analytic model may largely overestimates the intrinsic luminosity at large column densities. (2) Unabsorbed reflection components are commonly observed, suggesting that the tori are clumpy. (3) Most of CTAGNs show small scattering fractions (<0.5%) implying a buried AGN nature. (4) Comparison with the results obtained for Compton-thin AGNs (Kawamuro et al. 2016) suggests that the properties of these CTAGNs can be understood as a smooth extension from Compton-thin AGNs with heavier obscuration; we find no evidence that the bulk of the population of hard X-ray selected CTAGN is different from less obscured objects.