Abstract:
Hot gas density distributions can be fitted to the X-ray emission and absorption observations of the Milky Way to determine the mass and metallicity, mainly within 50 kpc.  We have now included optical depth effects in the critical O VII and O VIII lines and find the same result from three different data sets.  An extended spherical hot halo is the main mass component, containing  about 3-4E10 Msun within 250 kpc, significantly lower than the mass of missing baryons, about 1.7E11 Msun. The hot halo is rotating at 180 +/- 40 km/s within 50 kpc, the density declines as r^-3/2, and the metallicity is about half solar.  Adding a disk component improves the fit but it is a minor contributor to the total mass. The missing baryons most likely lie beyond the virial radius, probably 2-3 R200.  In nearby external galaxies, we detect a SZ signal when stacking the nearest dozen spiral galaxies with L ~ L*.  This signal suggests a gas mass of about 5E10 Msun within R200, similar to that found around the Milky Way.

Host: Paul Schechter