Abstract Details
| Name: Mukesh Singh Bisht Affiliation: Raman Research Institute Conference ID: ASI2025_47 Title : Origin of hot gas in the Circumgalactic Medium of the Milky Way Authors and Co-Authors : Mukesh Singh Bisht 1, Projjwal Banerjee 2, Biman B. Nath 1, Smita Mathur 3,4, Yuri Shchekinov 1 Abstract Type : Oral Abstract Category : Galaxies and Cosmology Abstract : The recent detection of hot gas, referred to as `super-virial' gas ($\sim 10^7$ K), in the Circumgalactic Medium (CGM) of the Milky Way has raised intriguing questions about its origin, geometry, and spatial distribution. This gas has been observed both in X-ray emission and absorption; in emission, it appears alongside `virial' gas ($\sim 10^6$ K), while in absorption, it has been identified through the detection of highly ionized species like SiXIV, NeX, and OVIII in the spectra of Quasars. Notably, the `emitting' super-virial gas and the `absorbing' super-virial gas have different origins. To demystify the origin and characteristics of hot gas, we have developed models for both emitting and absorbing super-virial gas. For the emitting gas, we adopt a `puffed-up disk' geometry based on the observed anticorrelation between Emission Measure (EM) and sin(b), where b is the Galactic latitude with a typical scale height of $1$ kpc and scale radius of $5$ kpc. This disk-like model explains the observed correlation between the EM of the super-virial and virial gas. We have also conducted hydrodynamical simulations of supernova (SNe)-driven disk-wide outflows to connect the origin of this gas to the outflows from SNe in the Milky Way's disk. For the absorbing super-virial gas, we propose that it originates from shocked ejecta in supernova remnants (SNRs) located in the extra-planar region surrounding the Milky Way's disk. The reverse shock in the supernova can heat the $\alpha$-enriched ejecta to very high temperatures ($\sim 10^7$ K). This model effectively accounts for the high column densities of H-like ions observed in absorption when the line of sight intersects such SNRs in the halo. Additionally, the supernova model explains the non-solar composition of the observed super-virial gas, as the shocked ejecta is \(\alpha\)-enriched and likely has super-solar characteristics. |