Self-gravitational collapse of a magnetized cloud core: high resolution simulations with three-dimensional MHD nested grid

Abstract

We investigate self-gravitational collapse of magnetized molecular cloud cores and formation of the outflow. We employ a nested grid in order to resolve fine structures of protostar and outflow generation, of which size is as small as 1 AU, and to follow the whole structure of the molecular cloud core, of which radius reaches 0.1–1 pc, simultaneously. The nested grid allows us to follow the evolution of the cloud core with the high dynamic range of 10 5–10 6 in the spatial resolution. In this paper, we introduce implementations of the self-gravitational MHD nested grid code and show applications to early stages in star formation: gravitational collapse of cloud core, “first core” formation, and bipolar outflow ejection. In both cases of single and binary star formation, magnetic fields play important role in the outflow formation. The outflow region has extremely low beta regions of β=10 −6–10 −3, and our code shows no sign of numerical instability even in these low-beta regions.