Brown Dwarfs from Turbulent Fragmentation

The origin of brown dwarfs (BDs) is an important component of the theory of star formation, because BDs are approximately as numerous as solar mass stars. It has been suggested that BDs originate from the gravitational fragmentation of protostellar disks, a very different mechanism from the formation of hydrogen burning stars. We propose that BDs are instead formed by the process of turbulent fragmentation, like more massive stars. In numerical simulations of turbulence and star formation we find that gravitationally unstable density peaks of BD mass are commonly formed by the turbulent flow. These density peaks collapse into BD mass objects with circumstellar disks, like more massive protostars. We rely on numerical experiments with very large resolution, achieved with adaptive mesh refinement (AMR). The turbulence simulation presented here is the first AMR turbulence experiment ever attempted and achieves an effective resolution of 1024^3 computational zones. The star formation simulation achieves an effective resolution of (10^6)^3 computational zones, from a cloud size of 5pc to protostellar disks resolved down to 1AU.