Does Our Galaxy have a Massive Dark Corona?

Abstract

The rotation curves of spiral galaxies indicate that most of them have massive dark coronas, and it seems likely that our Galaxy also has a dark corona. Our position in the galactic disk makes it difficult to measure the galactic rotation curve beyond about 20 kpc from the galactic center, but it does allow us to use several other indicators of the total galactic mass out to very large distances. I will review some of these indicators. The conclusion is that the Galaxy does indeed have a massive dark corona: the data are consistent with the enclosed mass within radius R increasing like M(R) ≈ R(kpc) × 1010M⊙, out to a radius of more than 100 kpc, and a total galactic mass of at least 12 × 1011M⊙.