Broadband X-ray properties of absorbed AGN

TL;DR

This study analyzes the broadband X-ray spectra of 33 absorbed Seyfert galaxies, revealing properties of their primary emission, reflection features, and the nature of their absorbing and reflecting media, supporting the unified AGN model.

Contribution

It provides detailed broadband X-ray spectral analysis of a complete absorbed AGN sample, identifying high energy cut-offs and exploring the origins of reflection and Fe K lines, with implications for AGN unification.

Findings

High energy cut-off in 30% of sources, below 150 keV.

Diagnostic NH vs Fobs plot for identifying Compton thick AGN.

No confirmation of the Iwasawa-Taniguchi effect.

Abstract

In this paper we report on the broadband X-ray properties of a complete sample of 33 absorbed Seyfert galaxies hard X-ray selected with integral. The high quality broadband spectra obtained with both xmm, and integral-IBIS data are well reproduced with an absorbed primary emission with a high energy cutoff and its scattered fraction below 2-3 keV, plus the Compton reflection features. A high energy cut-off is found in 30% of the sample, with an average value below 150 keV. The diagnostic plot NH vs Fobs(2-10 keV)/F(20-100 keV) allowed the isolation of the Compton thick objects, and may represent a useful tool for future hard X-ray observations of newly discovered AGN. We are unable to associate the reflection components with the absorbing gas as a torus, a more complex scenario being necessary. In the Compton thin sources, a fraction (but not all) of the Fe K line needs to be produced in a gas possibly associated with the optical Broad Line Region, responsible also for the absorption. We still need a Compton thick medium (not intercepting the line of sight) likely associated to a torus, which contributes to the Fe line intensity and produces the observed reflection continuum above 10 keV. The so-called Iwasawa-Taniguchi effect can not be confirmed with our data. Finally, the comparison with a sample of unobscured AGN shows that, type 1 and type 2 (once corrected for absorption) Seyfert are characterized by the same nuclear/accretion properties (luminosity, bolometric luminosity, Eddington ratio), supporting the "unified" view.