2006A&A...455..153M

We analysed the spectra from the XMM-Newton and the three longest Chandra observations of the Circinus Galaxy, the X-ray brightest, Compton-thick Seyfert 2 galaxy, to derive the physical and morphological parameters of the circumnuclear matter. We compare the line and continuum parameters with extensive calculations performed with the well-known photoionisation code CLOUDY. The line spectrum cannot be explained by a single zone, as three different reflecting regions are required. The first has low ionisation, accounting for the prominent iron Kα line, and is likely to be identified with the ``torus'' envisaged in unification models for Seyfert galaxies; a lower limit of 0.05pc to the distance of this matter from the nucleus has been estimated, using new constraints on the ionisation state of iron (≤FeX). The second zone is moderately ionised and optically thin (τ≃0.2), and it accounts for the oxygen to silicon lines. Finally, a third, highly ionised and optically thin reflector is required for the detection of the He-like iron line.