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تسجيل مستخدم جديدThe hot circumgalactic medium of the Milky Way: evidence for super-virial, virial, and sub-virial temperature, non-solar chemical composition, and non-thermal line broadening
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For the first time, we present the simultaneous detection and characterization of three distinct phases at $>10^5$ K in $z=0$ absorption, using deep $it{Chandra}$ observations toward Mrk 421. The extraordinarily high signal-to-noise ratio ($geqslant60$) of the spectra has allowed us to detect a $it{hot}$ phase of the Milky Way circumgalactic medium (CGM) at 3.2$^{+1.5}_{-0.5}times$ 10$^7$ K, coexisting with a $textit{warm-hot}$ phase at 1.5$pm$0.1$times$10$^6$ K and a $textit{warm}$ phase at 3.0$pm$0.4$times$10$^5$ K. The $textit{warm-hot}$ phase is at the virial temperature of the Galaxy, and the $textit{warm}$ phase may have cooled from the $textit{warm-hot}$ phase, but the super-virial $textit{hot}$ phase remains a mystery. We find that [C/O] in the $textit{warm}$ and $textit{warm-hot}$ phases, [Mg/O] in the $textit{warm-hot}$ phase and [Ne/O] in the $textit{hot}$ phase are super-solar, and the $textit{hot}$ and the $textit{warm-hot}$ phases are $alpha-$enhanced. Non-thermal line broadening is evident in the $textit{warm-hot}$ and the $textit{hot}$ phases and it dominates the total line broadening. Our results indicate that the $>10^5$ K CGM is a complex ecosystem. It provides insights on the thermal and chemical history of the Milky Way CGM, and theories of galaxy evolution.
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