Deep Chandra observations of diffuse hot plasma in M83

Abstract

ABSTRACT It is widely believed that galaxy formation and evolution is regulated by stellar mechanical feedback in forms of fast stellar winds and supernova explosions. However, the coupling of this feedback with the interstellar medium remains poorly understood. We examine how the coupling may be traced by diffuse soft X-ray emission in M83 – a nearby face-on spiral galaxy undergoing active star formation, based chiefly on 729 ks Chandra observations. Our main findings are (1) the X-ray emission is enhanced not only along the galaxy’s grand spiral arms, but also clearly in their downstreams; (2) the spectrum of the emission can be well characterized by a supersolar metallicity plasma with a lognormal temperature distribution, plus an X-ray absorption of a lognormal column density distribution; and (3) the intensity of the emission is strongly anticorrelated with the dust obscuration seen in optical images of the galaxy. These findings suggest (A) the morphology of the X-ray emission is likely due to the convolution of the feedback heating of the plasma with its thermal and dynamical evolution; (B) the X-ray emission, accounting for $\sim 10{{\ \rm per\ cent}}$ of the feedback energy input rate, probably traces only the high-energy tail of the radiation from the plasma; (C) a good fraction of the recent star-forming regions seems sufficiently energetic to produce multi-phased outflows, likely responsible for much of the dust obscuration and X-ray absorption. Direct confrontation of the findings with theories/simulations could help to understand the underlying astrophysics of the coupling and how the hot plasma shapes the interstellar medium.