No need for MACHOs in the halo

One interpretation of the more than dozen microlensing events seen in the direction of the LMC is a halo population of 0.5 M_⊙ MACHOs that accounts for about half of the mass of the Galaxy. Such an interpretation is not without its problems, and we show that LMC microlensing can be explained by a combination of dark components of the thick disk and spheroid in a viable and detailed model of the Galaxy. In our models, the total mass within 50 kpc is ∼10¹¹ M_⊙, about 60% of the value based on halo MACHO models, and the estimate for the lens mass is lower, 0.3 M_⊙ versus 0.5 M_⊙. The chemical evolution problems associated with the MACHO progenitors are not resolved. However, since the MACHO distribution does not trace the l/r² dark halo, which extends significantly beyond 50 kpc, the total baryon mass fraction of the Galaxy is reduced considerably, which lessens the problem.