Constraining the Milky Way Mass with Its Hot Gaseous Halo

We propose a novel method to constrain the Milky Way (MW) mass ${M}_{\mathrm{vir}}$ with its corona temperature observations. For a given corona density profile, one can derive its temperature distribution assuming a generalized equilibrium model with nonthermal pressure support. While the derived temperature profile decreases substantially with radius, the X-ray-emission-weighted average temperature, which depends most sensitively on ${M}_{\mathrm{vir}}$, is quite uniform toward different sight lines, consistent with X-ray observations. For a Navarro–Frenk–White (NFW) total matter distribution, the corona density profile should be cored, and we constrain ${M}_{\mathrm{vir}}=(1.19\mbox{--}2.95)\times {10}^{12}{M}_{\odot }$. For a total matter distribution contributed by an NFW dark matter profile and central baryons, the corona density profile should be cuspy and ${M}_{\mathrm{vir},\mathrm{dm}}=(1.34\mbox{--}5.44)\times {10}^{12}{M}_{\odot }$. Nonthermal pressure support leads to even higher values of ${M}_{\mathrm{vir}}$, while a lower MW mass may be possible if the corona is accelerating outward. This method is independent of the total corona mass, its metallicity, and temperature at very large radii.