Systematic Study of AGN Clumpy Tori with Broadband X-ray Spectroscopy: Updated Unified Picture of AGN Structure

TL;DR

This study systematically analyzes broadband X-ray spectra of 28 nearby AGNs using the XCLUMPY model, confirming key aspects of the unified AGN structure and revealing differences in line-of-sight properties between obscured and unobscured AGNs.

Contribution

It provides the largest sample analysis combining X-ray and infrared clumpy torus models, updating the unified AGN model with new observational insights.

Findings

Torus angular widths differ between infrared and X-ray data.

Line-of-sight $N_{H}/A_{V}$ ratios are similar to Galactic values in obscured AGNs.

Unobscured AGNs show smaller $N_{H}/A_{V}$ ratios than Galactic.

Abstract

We present the results of a systematic, broadband X-ray spectral analysis of nearby active galactic nuclei (AGNs) with the X-ray clumpy torus model (XCLUMPY; Tanimoto et al. 2019). By adding 16 AGNs newly analyzed in this paper, we study total 28 AGNs including unabsorbed and absorbed AGNs taken from Ichikawa et al. (2015) and Garc\'ia-Bernete et al. (2019). This is the largest sample whose X-ray and infrared spectra are analyzed by the clumpy torus models XCLUMPY and CLUMPY (Nenkova et al. 2008), respectively. The relation between the Eddington ratio and the torus covering factor determined from the X-ray torus parameters of each object follows the trend found by Ricci et al. (2017) based on a statistical analysis. We confirm the results by Tanimoto et al. (2020) that (1) the torus angular widths determined by the infrared data are larger than those by the X-ray data and that (2) the ratios of the hydrogen column density to V-band extinction ($N_{\rm H}/A_{\rm V}$) along the line of sight in obscured AGNs are similar to the Galactic value on average. Unobscured AGNs show apparently smaller line-of-sight $N_{\rm H}/A_{\rm V}$ ratios than the Galactic one. Our findings can be well explained by an updated unified picture of AGN structure including a dusty torus, dusty polar outflows, and dust-free gas, where the inclination determines the X-ray and optical classifications and observed torus properties in the X-ray and infrared bands.