The Milky Way galaxy is surrounded by a circumgalactic medium (CGM) that may play a key role in galaxy evolution as the source of gas for star formation and a repository of metals and energy produced by star formation and nuclear activity. The CGM may also be a repository for baryons seen in the early universe, but undetected locally. The CGM has an ionized component at temperatures near 2×106~K studied primarily in the soft X-ray band. Here we report a survey of the southern Galactic sky with a soft X-ray spectrometer optimized to study diffuse soft X-ray emission. The X-ray emission is best fit with a disc-like model based on the radial profile of the surface density of molecular hydrogen, a tracer of star formation, suggesting that the X-ray emission is predominantly from hot plasma produced via stellar feedback. Strong variations in the X-ray emission on angular scales of ∼10∘ indicate that the CGM is clumpy. Addition of an extended, and possibly massive, halo component is needed to match the halo density inferred from other observations.
@article{arxiv.2011.00126,
title = {A disk-dominated and clumpy circumgalactic medium of the Milky Way seen in X-ray emission},
author = {P. Kaaret and D. Koutroumpa and K. D. Kuntz and K. Jahoda and J. Bluem and H. Gulick and E. Hodges-Kluck and D. M. LaRocca and R. Ringuette and A. Zajczyk},
journal= {arXiv preprint arXiv:2011.00126},
year = {2020}
}