Bondi-Hoyle accretion in a turbulent, magnetized medium

We present simulations of accretion on to point masses embedded in an isothermal gas that is magnetized and supersonically turbulent, as occurs for protostars in molecular clouds. We use the ORION2 adaptive mesh refinement (AMR) code to carry out ideal magnetohydrodynamic simulations for an rms Mach number M-rms = 5 and a wide range of Alfven Mach numbers. We find that the probability density functions for accretion rates in all models are very wide (+/- 0.5 dex) and asymmetric, tilted to low accretion rates; the mean accretion rate is about twice the median. We find that the results of Lee et al. for magnetized Bondi-Hoyle accretion with the relative velocity parallel to the field describe our results to within a factor of 2, and we suggest that this should be valid at least fo rM(rms) less than or similar to 10. Our results show that turbulent magnetic fields of the strength observed in molecular clouds reduce the accretion rate relative to the classical Bondi-Hoyle rate by a factor of a few for Alfven Mach numbers of order unity, but this is comparable to the reduction due to supersonic hydrodynamic turbulence alone. This reduction in accretion rates should be taken into account in analytic models of competitive accretion and analytic estimates of the accretion luminosities of young stellar objects in molecular clouds.