The soft X-ray background with Suzaku. II. Supervirial temperature bubbles?

The article focuses on the detection and analysis of a hot, ∼0.8 keV collisional-ionization-equilibrium (CIE) plasma component in the soft X-ray background of the Milky Way, based on 130 Suzaku X-ray observations covering galactic longitudes 75°–285° and latitudes |b| > 15°. This supervirial temperature component, distinct from the standard local hot bubble (LHB) and Milky Way halo (MWH) plasmas, shows significant spatial variation with higher emission measures toward lower galactic latitudes and is especially enhanced in the direction of the Orion–Eridanus superbubble. The study accounts for possible contamination from solar wind charge exchange (SWCX), unresolved stars, and background galaxy groups, concluding that the 0.8 keV component is unlikely to be dominated by these sources. The authors suggest that this hot plasma is likely heated by supernovae in the Galactic disk and may be associated with Galactic fountains, contributing to the feedback processes influencing the interstellar medium and galaxy evolution.