Our study focuses on characterizing the highly ionized gas within the Milky Way's (MW) Circumgalactic Medium (CGM) that gives rise to ionic transitions in the X-ray band 2 - 25 \AA. Utilizing stacked \Chandra/\ACISS\ \MEG\ and \LETG\ spectra toward QSO sightlines, we employ the self-consistent hybrid ionization code PHASE to model our data. The stacked spectra are optimally described by three distinct gas phase components: a \warm\ (\logT\ ∼ 5.5), \warmhot\ (\logT\ ∼6), and \hot\ (\logT\ ∼ 7.5) components. These findings confirm the presence of the \hot\ component in the MW's CGM indicating its coexistence with a \warm\ and a \warmhot\ gas phases. We find this \hot\ component to be homogeneous in temperature but inhomogeneous in column density. The gas in the \hot\ component requires over-abundances relative to solar to be consistent with the Dispersion Measure (DM) from the Galactic halo reported in the literature. {For the hot phase we estimated a DM = 55.1−23.7+29.9 pc cm−3}. We conclude that this phase is either enriched in Oxygen, Silicon, and Sulfur, or has metallicity {over 6} times solar value, or a combination of both. We do not detect Fe L-shell absorption lines, implying O/Fe ≥ 4. The non-solar abundance ratios found in the super-virial gas component in the Galactic halo suggest that this phase arises from Galactic feedback.
@article{arxiv.2407.16784,
title = {A Sub-solar Fe/O, logT~7.5 Gas Component Permeating the Milky Way's CGM},
author = {Armando Lara-DI and Yair Krongold and Smita Mathur and Sanskriti Das and Anjali Gupta and O. Segura Montero},
journal= {arXiv preprint arXiv:2407.16784},
year = {2024}
}