| Name: Mukesh Singh Bisht |
| Affiliation: Raman Research Institute |
| Conference ID: ASI2026_81 |
| Title: Revealing the Thermal and Chemical Inhomogeneity of the Milky Way’s Hot Circumgalactic Medium |
| Abstract Type: Poster |
| Abstract Category: Galaxies and Cosmology |
| Author(s) and Co-Author(s) with Affiliation: Mukesh Singh Bisht(Raman Research Institute, Bangalore- 560080, India), Sanskriti Das(Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, CA- 94305, USA), Smita Mathur(Ohio State University, Columbus, OH- 43210, USA), Manami Roy(Ohio State University, Columbus, OH- 43210, USA), Yair Krongold(Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Mexico City- 04510, Mexico), Anjali Gupta(Columbus State Community College, Columbus, OH- 43210, USA) |
| Abstract: The presence of virial-temperature gas ($\sim 10^6$ K) in the circumgalactic medium (CGM) of the Milky Way is relatively well established. However, the recent discovery of an even hotter temperature gas, known as `super-virial' gas ($\sim 10^7$ K), is particularly intriguing. This gas has been detected in both X-ray emission and absorption. While the emitting super-virial gas covers nearly 80% of the sky, absorption detections remain limited to only a few sightlines, suggesting that its spatial distribution and origin are not yet well constrained. The emitting and absorbing components represent physically distinct gas phases: the emitting gas is commonly attributed to stellar-driven feedback from the Galactic disk, whereas the origin of the absorbing component remains unclear. Studying this gas along previously unexplored sightlines is therefore crucial for constraining its properties and understanding its role in the Milky Way CGM.
In this conference, I will present new X-ray absorption measurements of super-virial gas along two independent sightlines through the Milky Way CGM. Along the sightline toward PKS 2155–304, we detect MgXII and SiXIV absorption lines—unambiguous tracers of super-virial gas—together with several lower-ionization species. These observations reveal, for the first time, the presence of four distinct temperature phases along this sightline. We also detect super-virial gas along the sightline toward 3C 273, where X-ray absorption reveals three distinct temperature components, including a super-virial phase. These studies, including this work, show that the X-ray–absorbing super-virial gas is both thermally and chemically inhomogeneous and likely widespread, highlighting the need for detailed absorption studies along multiple lines of sight. These findings place new constraints on the multiphase structure of the Milky Way’s CGM and demonstrate the importance of X-ray absorption in probing its hottest components. |
