Mass models for the Milky Way

The bumps and wiggles in the terminal velocity curve correspond to known spiral features (e.g., the Centaurus arm is a ~50% overdensity). The rotation curve switches between positive and negative over scales of hundreds of parsecs. The rms amplitude <|dV/dR|^2^>^1/2^, implying that commonly neglected terms in the Jeans equations may be nonnegligible.

The spherically averaged local dark matter density is {rho}_0,DM_~0.009M_{sun}_/pc3 (0.34GeV/cm3). Adiabatic compression of the dark matter halo may help reconcile the Milky Way with the c-V_200_ relation expected in {Lambda}CDM while also helping to mitigate the too-big-to-fail problem, but it remains difficult to reconcile the inner bulge/bar-dominated region with a cuspy halo. We note that NGC 3521 is a near twin to the Milky Way, having a similar luminosity, scale length, and rotation curve.