Origin of ‘super-virial’ gas in the Circumgalactic medium of Milky way

Mukesh Singh Bisht1, Biman B Nath1, Projjwal Banerjee2

Raman Research Institute1, IIT Palakkad2

Circumgalactic medium (CGM) is the gaseous component surrounding the Interstellar medium (ISM) of the Galaxy. The gas in CGM is diffuse and multiphase with typical density ranging from 10-4 - 10-1 cm-3 and temperature ranging from cold phase (~104K), warm phase (~105 K) to the virial/hot phase (~106K). Recent observations, however, have detected an even hotter gas/phase (~107 K) in the CGM. This ‘super-virial’ gas is detected in emission over the entire sky as well as in absorption along a few lines of sight. Further analysis by various authors suggest the ‘emitting super-virial gas’ and the ‘absorbing super-virial gas’ have different physical origins. In our work, we suggest that the ‘emitting super-virial gas’ is the result of disk-wide outflows from the Milky Way by performing hydrodynamic simulation of the outflows. We also suggest that the supernova in the Halo/CGM can mimic the signs of super-virial gas seen in absorption if the line of sight pass through such supernova remnant in the CGM. We numerically evolve the supernova and calculate column density of various ions and compare with the observations.