Suzaku observations of hard X-ray selected Seyfert 2 galaxies

TL;DR

This study uses Suzaku to observe five nearby Seyfert 2 galaxies, revealing diverse obscuration features, complex spectra, and the presence of reflection and thermal components, challenging simple unified models.

Contribution

First detailed broad-band X-ray analysis of multiple Seyfert 2 galaxies with Suzaku, highlighting spectral diversity and complexities in obscuration and emission components.

Findings

Detection of heavy obscuration and reflection-dominated spectra.

Presence of strong iron Kalpha lines in Compton thick AGN.

Soft X-ray emission varies and may originate from scattered, leaked, or thermal sources.

Abstract

We present Suzaku observations of five hard X-ray selected nearby Seyfert 2 galaxies. All the sources were clearly detected with the pin Hard X-ray Detector up to several tens of keV, allowing for a fairly good characterization of the broad-band X-ray continuum. We find that a unique model, even including multiple components, fails to represent the spectra of all the sources. Heavy obscuration manifests itself in different flavours. For two sources there is evidence for a reflection dominated continuum; among the other three, one is "mildly" Compton thick (N_H ~ 10^24 cm-2), while the remaining two are heavily obscured (N_H ~ 10^23.5 cm-2), but Compton thin. Strong, narrow, iron Kalpha lines (EW ~ 1-2 keV) due to neutral or mildly ionized gas, are detected in Compton thick AGN. In all of them the Kalpha line is accompanied by the Kbeta. The intensity and shape of the soft X-ray spectrum are different from object to object. Soft X--rays may originate from a nuclear component scattered off, or leaking through, the X-ray absorber, plus thermal X-rays from the host galaxy. Emission from circumnuclear gas photoionized by the active nucleus, parameterized with a power law plus individual narrow Gaussian lines, also provides an acceptable description of the soft X-ray spectra. The limited Suzaku XIS CCD energy resolution does not allow us to draw firm conclusions on the origin of the soft X--ray emission. We briefly discuss our findings in the light of AGN Unified model and the geometry of the obscuring gas.