ROSAT PSPC X-ray observations of the nearby spiral galaxy M83

TL;DR

This study uses ROSAT PSPC X-ray observations to analyze the diffuse and point-source X-ray emission in the galaxy M83, revealing a two-temperature plasma halo and linking star formation to halo structure.

Contribution

First characterization of M83's diffuse X-ray spectrum as a two-temperature plasma with a soft halo and hot disk component, highlighting magnetic fields' role in halo evolution.

Findings

Detected 13 X-ray point sources, 10 new discoveries.

Identified a large spherical gas halo of 10-15 kpc radius.

Established a connection between star formation and X-ray emission processes.

Abstract

The nearly face-on SBc galaxy M83 (NGC 5236) was observed for 25 ksec with the ROSAT PSPC. We detected 13 point-like sources in this galaxy, 10 of which were previously unknown. We measured extended X-ray radiation from almost the whole optically visible galaxy. Comparing the diffuse soft and hard X-ray emission components, we observed a different asymmetric distribution and a slower radial decrease of the intensity profile of the soft X-ray emission. Both these results support the existence of a huge spherical gas halo of 10-15 kpc radius. On the other hand, the radial scale lengths of the hard X-ray radiation, that of the thermal radio emission and the profile of the optical surface brightness are similar, favouring the idea that all these emission processes are connected to star formation in the galaxy's disk. M83 is the first face-on galaxy where the diffuse X-ray emission spectrum can be characterized by a two-temperature thermal plasma: a soft X-ray emitting warm `halo component' and an internally absorbed hot `disk component' which is dominating the emission in the hard (0.5-2.0 keV) ROSAT energy range. The combination of X-ray and radio polarization observations allows an estimate of the plasma parameter beta = U_therm/U_magn which is found to be 0.2+/-0.1. This result supports the hypothesis that magnetic fields play an important role for the evolution and structure of galactic gas haloes. The high energy input rate in the active star-forming disk of M83 seems to be responsible for the outflow of hot gas and the halo formation.