Superbubble Growth, Energetics, and Breakout with the Line Emission Mapper

Massive star clusters blow giant hot bubbles in the interstellar medium through a combination of stellar winds and supernovae. These superbubbles extinguish star formation in the natal cloud and can regulate or enhance star formation in neighboring regions, as well as blow out of the disk to drive a galactic fountain or wind. Superbubbles are widely accepted as a key element of stellar feedback, but their growth, radiative and mechanical luminosity, and ultimate impact on the disk and halo remain poorly quantified in large part because of the lack of direct measurements of the temperature, density, pressure, and metallicity of the hot gas within. These problems are compounded by the lack of knowledge of the ionization state, the prevalence of nonthermal emission, and the significant contribution of charge exchange to key X-ray diagnostic lines. After more than twenty years of Chandra and XMM-Newton observations, the key limiting factor is spectral resolution. We will show how the Line Emission Mapper (LEM) Probe (http://lem.cfa.harvard.edu/) can map these properties in a population of Local Group superbubbles via a focused, feasible, and foundational observing program.