On the Consistency between the Outer Rotation Curve of the Galaxy and the Microlensing Rate towards the Large Magellanic Cloud

Recent determination of the outer rotation curve of the Galaxy suggests that the total Galactic mass is likely to concentrate into a region of radius $\sim2R_0$. If this finding is correct, the previously estimated optical depth of microlensing events towards the Large Magellanic Cloud (LMC) should be correspondingly reduced. It appears that a truncated Galactic halo model instead of the standard isothermal one extending to LMC accounts naturally for the reported microlensing rate by the MACHO collaboration. Such an explanation is indeed obvious yet has been overlooked in the past.