The Milky Way’s Kiloparsec‐Scale Wind: A Hybrid Cosmic‐Ray and Thermally Driven Outflow

Abstract

We apply a wind model, driven by combined cosmic-ray and thermal-gas\npressure, to the Milky Way, and show that the observed Galactic diffuse soft\nX-ray emission can be better explained by a wind than by previous static gas\nmodels. We find that cosmic-ray pressure is essential to driving the observed\nwind. Having thus defined a "best-fit" model for a Galactic wind, we explore\nvariations in the base parameters and show how the wind's properties vary with\nchanges in gas pressure, cosmic-ray pressure and density. We demonstrate the\nimportance of cosmic rays in launching winds, and the effect cosmic rays have\non wind dynamics. In addition, this model adds support to the hypothesis of\nBreitschwerdt and collaborators that such a wind may help explain the\nrelatively small gradient observed in gamma-ray emission as a function of\ngalactocentric radius.\n