Thermal and non-thermal X-ray emission from stellar clusters and superbubbles

Abstract

Massive stellar clusters inject significant mass and energy into their surroundings driving superbubbles, 100–1000 pc diameter shells of swept-up interstellar material that contain a hot ($10^{6}$ K), shock-heated gas. Analytically, the evolution of these objects is usually described as an expanding, pressure-driven bubble. However, in the 90s discrepancies between predictions of the pressure-driven model and X-ray observations of superbubbles were observed. Resolutions to these discrepancies were proposed, mainly through modifications to the model, though it wasn’t until the advent of Chandra, XMM-Newton, and Suzaku that these could be observationally tested, with advances in numerical modelling also providing valuable insight. Here I review X-ray observations of superbubbles and their massive stellar clusters and describe how their thermal and non-thermal X-ray emission have helped the understanding of the physical properties and evolution of these objects. Future prospects with the next generation of X-ray observatories are also discussed.