The End of the MACHO Era: Limits on Halo Dark Matter from Stellar Halo Wide Binaries

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Abstract
We simulate the evolution of halo wide binaries in the presence of the massive compact halo objects (MACHOs) and compare our results to the sample of wide binaries in a companion paper. The observed distribution is well fitted by a single power law for angular separations, 3".5 < Delta theta < 900", whereas the simulated distributions show a break in the power law whose location depends on the MACHO mass and density. This allows us to place upper limits on the density of MACHOs as a function of their assumed mass. At the 95% confidence level, we exclude MACHOs with masses M > 43 M-circle dot at the standard local halo density rho(H). This all but removes the last permitted window for a full MACHO halo for masses M > 10(-7.5) M-circle dot.