Interestingly, M31, one of the major two massive galaxies in the Local Group, lies on this curve.

These facts imply that the mass distribution in the Galaxy is an isolated system from the other members in so far as it is observed within $\sim 150$ kpc radius. Hence, if it is gravitationally bound to the Local Group, there must exist a much larger amount of dark mass than the dark halo of the Galaxy, filling the entire Local Group.

Discussion
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Inner vs Outer Rotation Curves
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We have compared rotation curves based on the three dark halo models, isothermal, NFW, and Burkert, with the observed Galacto-Local Group rotation curve. In the inner Galaxy at $R<\sim 10$ kpc, the disk and bulge are the major constituents of the mass, and therefore, the rotation velocity is little affected by the dark halo. In the outer disk, the dark halo contribution becomes significant. However, the shape of the rotation curve is not sensitive to the halo models at $R\sim 10-20 $ kpc, which is almost flat in any model, and the discrimination among the models is again difficult.

We here note that, for such reasons, there have been many studies utilizing dwarf 