The end of the MACHO era:: Limits on halo dark matter from stellar halo wide binaries

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.