Deep X-ray spectroscopy and imaging of the Seyfert 2 galaxy, ESO 138-G001

TL;DR

This study analyzes X-ray data from ESO 138-G001, revealing a complex, inhomogeneous Compton-thick absorber and soft X-ray emission mainly driven by photoionisation, advancing understanding of Seyfert 2 galaxy circumnuclear environments.

Contribution

It provides the first detailed spectral and imaging analysis of ESO 138-G001, highlighting the inhomogeneous nature of the obscuring torus and the ionization mechanisms of soft X-ray emission.

Findings

Confirmed Compton-thick absorption in ESO 138-G001.

Detected inhomogeneous torus with variable column density.

Soft X-ray emission dominated by photoionisation processes.

Abstract

We present a spectral and imaging analysis of the XMM-Newton and Chandra observations of the Seyfert 2 galaxy ESO138-G001, with the aim of characterizing the circumnuclear material responsible for the soft (0.3-2.0 keV) and hard (5-10 keV) X-ray emission. We confirm that the source is absorbed by Compton-thick gas. However, if a self-consistent model of reprocessing from cold toroidal material is used (MYTorus), a possible scenario requires the absorber to be inhomogenous, its column density along the line of sight being larger than the average column density integrated over all lines- of-sight through the torus. The iron emission line may be produced by moderately ionised iron (FeXII-FeXIII), as suggested by the shifted centroid energy and the low K{\beta}/K{\alpha} flux ratio. The soft X-ray emission is dominated by emission features, whose main excitation mechanism appears to be photoionisation, as confirmed by line diagnostics and the use of self-consistent models (CLOUDY).