X-ray observations of the Compton-thick Seyfert 2 galaxy, NGC 5643

TL;DR

This study uses XMM-Newton observations to determine that NGC 5643 is a Compton-thick AGN with a soft X-ray excess mainly from photoionized matter, and also analyzes other X-ray sources in the field.

Contribution

First detailed X-ray spectral analysis confirming the Compton-thick nature of NGC 5643 and characterizing its soft X-ray emission origin.

Findings

NGC 5643 is confirmed as a Compton-thick AGN.

Soft X-ray emission is primarily from photoionized matter.

The ULX NGC 5643 X-1 is less luminous than in 2003.

Abstract

We present results from a ~55 ks long XMM-Newton observation of the obscured AGN, NGC 5643, performed in July 2009. A previous, shorter (about 10 ks) XMM-Newton observation in February 2003 had left two major issues open, the nature of the hard X-ray emission (Compton-thin vs Compton-thick) and of the soft X-ray excess (photoionized vs collisionally ionized matter). The new observation shows that the source is Compton-thick and that the dominant contribution to the soft X-ray emission is by photoionized matter (even if it is still unclear whether collisionally ionized matter may contribute as well). We also studied three bright X-ray sources that are in the field of NGC 5643. The ULX NGC 5643 X-1 was confirmed to be very luminous, even if more than a factor 2 fainter than in 2003. We then provided the first high quality spectrum of the cluster of galaxies Abell 3602. The last source, CXOJ143244.5-442020, is likely an unobscured AGN, possibly belonging to Abell 3602.