X-ray spectroscopy of the starburst feedback in 30 Doradus

TL;DR

This study uses X-ray spectroscopy of 30 Doradus to analyze hot plasma properties, revealing complexities like non-isothermality, metal enrichment, and potential cosmic-ray acceleration, advancing understanding of starburst feedback.

Contribution

It introduces a novel log-normal modeling approach for X-ray spectral analysis of giant HII regions, accounting for plasma and absorption distributions.

Findings

Plasma metal abundances match expectations from stellar ejecta.

Total plasma mass shows ~55% mass-loading from ambient medium.

Evidence suggests non-thermal X-ray component and cosmic-ray acceleration.

Abstract

X-ray observations provide a potentially powerful tool to study starburst feedback. The analysis and interpretation of such observations remain challenging, however, due to various complications, including the non-isothermality of the diffuse hot plasma and the inhomogeneity of the foreground absorption. We here illustrate such complications and a way to mitigate their effects by presenting an X-ray spectroscopy of the 30 Doradus nebula in the Large Magellanic Clouds, based on a 100 ks Suzaku observation. We measure the thermal and chemical properties of the hot plasma and quantitatively confront them with the feedback expected from embedded massive stars. We find that our spatially resolved measurements can be well reproduced by a global modeling of the nebula with a log-normal temperature distribution of the plasma emission measure and a log-normal foreground absorption distribution. The metal abundances and total mass of the plasma are consistent with the chemically enriched mass ejection expected from the central OB association and a ~55% mass-loading from the ambient medium. The total thermal energy of the plasma is smaller than what is expected from a simple superbubble model, demonstrating that important channels of energy loss are not accounted for. Our analysis indeed shows tentative evidence for a diffuse non-thermal X-ray component, indicating that cosmic-ray acceleration needs to be considered in such a young starburst region. Finally, we suggest that the log-normal modeling may be suitable for the X-ray spectral analysis of other giant HII regions, especially when spatially resolved spectroscopy is not practical.