The Integrated Diffuse X-ray Emission of the Carina Nebula Compared to Other Massive Star-forming Regions

TL;DR

This study compares the diffuse X-ray emission of the Carina Nebula with other massive star-forming regions, revealing common thermal components, shock evidence, and potential charge exchange processes at hot-cold interfaces.

Contribution

It provides a comparative analysis of diffuse X-ray emission across multiple star-forming regions, highlighting spectral components and shock phenomena not previously characterized in detail.

Findings

All regions require at least two thermal plasma components.

Evidence of non-equilibrium ionization indicating recent shocks.

Detection of nonthermal X-ray emission likely from a recent supernova.

Abstract

The Chandra Carina Complex Project (CCCP) has shown that the Carina Nebula displays bright, spatially-complex soft diffuse X-ray emission. Here we `sum up' the CCCP diffuse emission work by comparing the global morphology and spectrum of Carina's diffuse X-ray emission to other famous sites of massive star formation with pronounced diffuse X-ray emission: M17, NGC 3576, NGC 3603, and 30 Doradus. All spectral models require at least two diffuse thermal plasma components to achieve adequate spectral fits, a softer component with kT = 0.2--0.6 keV and a harder component with kT = 0.5--0.9 keV. In several cases these hot plasmas appear to be in a state of non-equilibrium ionization that may indicate recent and current strong shocks. A cavity north of the embedded giant HII region NGC 3576 is the only region studied here that exhibits hard diffuse X-ray emission; this emission appears to be nonthermal and is likely due to a recent cavity supernova, as evidenced by a previously-known pulsar and newly-discovered pulsar wind nebula also seen in this cavity. All of these targets exhibit X-ray emission lines that are not well-modeled by variable-abundance thermal plasmas and that might be attributed to charge exchange at the shock between the hot, tenuous, X-ray-emitting plasma and cold, dense molecular material; this is likely evidence for dust destruction at the many hot/cold interfaces that characterize massive star-forming regions.