Formation and early evolution of circumstellar discs in turbulent molecular cloud cores

We investigate the formation and evolution of circumstellar discs in turbulent cloud cores until several 10(4) yr after protostar formation using smoothed particle hydrodynamics (SPH) calculations. The formation and evolution process of circumstellar disc in turbulent cloud cores differs substantially from that in rigidly rotating cloud cores. In turbulent cloud cores, a filamentary structure appears before the protostar formation and the protostar forms in the filament. If the turbulence is initially sufficiently strong, the remaining filament twists around the protostar and directly becomes a rotation-supported disc. Upon formation, the disc orientation is generally misaligned with the angular momentum of its host cloud core and it dynamically varies during the main accretion phase, even though the turbulence is weak. This is because the angular momentum of the entire cloud core is mainly determined by the large-scale velocity field whose wavelength is comparable to the cloud scale, whereas the angular momentum of the disc is determined by the local velocity field where the protostar forms and these two velocity fields do not correlate with each other. In the case of disc evolution in a binary or multiple stars, the discs are misaligned with each other at least during the main accretion phase, because there is no correlation between the velocity fields around the position where each protostar forms. In addition, each disc is also misaligned with the binary orbital plane. Such misalignment can explain the recent observations of misaligned discs and misaligned protostellar outflows.