2012/11/05 by Taotao Fang, James S. Bullock, James Bullock +1 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Baryon #Dwarf galaxy problem #Electrical and Electromagnetic Research #Galactic corona #Galactic halo #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Halo #Hydrostatic equilibrium #Milky Way #astro-ph.CO #astro-ph.GA #astro-ph.HE
paper · pdf · doi:10.1088/0004-637x/762/1/20
8 pages, 4 figures, accepted for publication in ApJ
arxiv created 2012/11/05 · openalex publication_date 2012/12/12 · arxiv updated 2015/06/12 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
The Milky Way appears to be missing baryons, as the observed mass in stars and gas is well below the cosmic mean. One possibility is that a substantial fraction of the Galaxy's baryons are embedded within an extended, million-degree hot halo, an idea supported indirectly by observations of warm gas clouds in the halo and gas-free dwarf spheroidal satellites. X-ray observations have established that hot gas does exist in our Galaxy beyond the local hot bubble; however, it may be distributed in a hot disk configuration. Moreover, recent investigations into the X-ray constraints have suggested that any Galactic corona must be insignificant. Here we re-examine the observational data, particularly in the X-ray and radio bands, in order to determine whether it is possible for a substantial fraction of the Galaxy's baryons to exist in ∼10 6 K gas. In agreement with past studies, we find that a baryonically closed halo is clearly ruled out if one assumes that the hot corona is distributed with a cuspy Navarro–Frenk–White profile. However, if the hot corona of the galaxy is in an extended, low-density distribution with a large central core, as expected for an adiabatic gas in hydrostatic equilibrium, then it may contain up to 10 11 M ☉ of material, possibly accounting for all of the missing Galactic baryons. We briefly discuss some potential avenues for discriminating between a massive, extended hot halo and a local hot disk.