Formation and Early Evolution of Circumstellar Disks in Turbulent Molecular Cloud Cores

TL;DR

This study uses SPH simulations to explore how turbulent molecular cloud cores form and evolve circumstellar disks, revealing their filamentary origins, misalignments, and dynamic behaviors during early star formation.

Contribution

It demonstrates the significant impact of turbulence on disk formation, orientation, and evolution, highlighting differences from rigidly rotating cloud cores and explaining observed misalignments.

Findings

Filamentary structures precede disk formation in turbulent cores.

Disks often form misaligned with the host cloud's angular momentum.

Misalignments persist during the main accretion phase and can explain observations.

Abstract

We investigate the formation and evolution of circumstellar disks in turbulent cloud cores until several 104 years after protostar formation using smoothed particle hydrodynamics (SPH) calculations. The formation and evolution process of circumstellar disk 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 disk. Upon formation, the disk 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 disk 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 disk evolution in a binary or multiple stars, the disks 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 disk is also misaligned with the binary orbital plane. Such misalignment can explain the recent observations of misaligned disks and misaligned protostellar outflows.