Abstract

Contributed Talk - Splinter StarFormation   (MW-1250)

Linking Magnetic Flux Transport to Protostellar Disk Sizes

Shang-Jing Lin; Hsi-Wei Yen
University of Cologne / ASIAA

The magnetic field plays a crucial role at all stages of the star formation process, from supporting dense cores against gravitational collapse to transporting angular momentum during protostellar disk formation. The non-ideal MHD effects, such as ambipolar diffusion, are theoretically expected to reduce the efficiency of magnetic braking and enhance the angular momentum transport inward to form sizeable disks. However, observational constraints on the magnetic field strength at envelope scale are still highly uncertain, leaving the evolution of magnetic flux from cores to envelopes and the impact of non-ideal MHD effects poorly understood. In this study, we analyze the ALMA archival data of 0.85 mm polarized emission and 13CO (2-1) emission of a Class I protostar, HOPS-370. We construct a 3D solenoidal magnetic field model and envelope+disk kinematical model to fit the observational data. From the force balance, we estimate the magnetic field strength and compare the mass-to-flux ratio from the core to envelope and disk size. Our results suggest that an inward increase in the mass-to-flux ratio would result in a disk size approaching the hydrodynamic limit, supporting that magnetic diffusion by non-ideal MHD effects reduces magnetic braking efficiency.