Resolving the Prototypical Galactic Wind in M82

Starburst-driven winds are an important feedback mechanism for regulating star formation and redistributing mass and metals within and beyond galaxies. While hot wind models assume that most of the energy is carried by the hot gas in multi-phase outflows, low energy resolution CCD measurements provide poor constraints on the total energy and amount of mass that can escape the galaxy. The prototypical starburst wind in M82 is among the few cases where we can use grating spectroscopy to measure the kinematics of the hot phase. Here we analyze deep archival observations of the hot outflow in M82 from the Reflection Grating Spectrometer on XMM-Newton. We characterize the instrumental line broadening on a range of spatial scales, and we constrain the intrinsic line broadening from turbulent and bulk motions in the extended wind. These results will provide constraints on galactic wind models and inform upcoming analyses of the outflow kinematics in M82 with the Resolve calorimeter spectrometer on XRISM.