The Milky Way's Hot Halo
Abstract
Extended gaseous halos near the virial temperature (~3E6 K) have been detected from X-ray emission and absorption in the Milky Way, and from X-ray emission around external galaxies. In the Milky Way, the gas is extended to at least 20-50 kpc and likely extends to the virial radius (250 kpc), where the mass would be approximately 3E10 Msun, nearly comparable to the stellar mass. The metallicity (from O), has a value of 0.2-0.9 Solar, showing evidence for feedback since its original pristine state. There is enhanced emission from the Fermi Bubbles, suggesting modest shock heating of the halo gas. In external spirals, similar hot halos are observed, and in galaxies a few times more massive than the Milky Way, gas is detected to about 130 kpc when the systems are stacked. The extended hot halo gas masses are comparable to the stellar mass at the virial radius but do not account for the missing baryons. If these hot gas halos are extrapolated to about twice the virial radius, the missing baryons would be accounted for.
- Publication:
-
American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020
- Bibcode:
- 2020AAS...23513806B