Probing AGN Inner Structure with X-ray Obscured Type 1 AGN

TL;DR

This study compares properties of X-ray obscured and unobscured broad-line AGN, revealing differences in black hole mass, Eddington ratio, and obscuration characteristics, supporting a multi-component, clumpy torus model with inclination-based classification.

Contribution

It provides observational evidence linking X-ray obscuration with optical dust extinction and intermediate inclination angles in a unified AGN model.

Findings

BLAGN2 have broader emission lines and higher black hole masses.

X-ray obscuration correlates with optical dust extinction.

Results support a multi-component, clumpy torus model.

Abstract

Using the X-ray-selected active galactic nuclei (AGN) from the XMM-XXL north survey and the SDSS Baryon Oscillation Spectroscopic Survey (BOSS) spectroscopic follow-up of them, we compare the properties of X-ray unobscured and obscured broad-line AGN (BLAGN1 and BLAGN2; $N_\textrm{H}$below and above $10^{21.5}$ cm$^{-2}$), including their X-ray luminosity $L_X$, black hole mass, Eddington ratio $\lambda_{\textrm{Edd}}$, optical continuum and line features. We find that BLAGN2 have systematically larger broad line widths and hence apparently higher (lower) $M_{\textrm{BH}}$ ($\lambda_{\textrm{Edd}}$) than BLAGN1. We also find that the X-ray obscuration in BLAGN tends to coincide with optical dust extinction, which is optically thinner than that in narrow-line AGN (NLAGN) and likely partial-covering to the broad line region. All the results can be explained in the framework of a multi-component, clumpy torus model by interpreting BLAGN2 as an intermediate type between BLAGN1 and NLAGN in terms of an intermediate inclination angle.