Oral Presentation

Importance of magnetic field orientation and strength in disk formation from observational perspective

Author(s): Hsi-Wei Yen (ASIAA) et al.

Presenter: Hsi-Wei Yen (ASIAA)

Disks around young stars are site of planet formation. Several mechanisms are proposed to enable formation of sizable disks around protostars in magnetized dense cores, such as misalignment between the magnetic field and rotational axis in a dense core, non-ideal MHD effects, etc. In this presentation, I will discuss the importance of magnetic field orientation and non-ideal MHD effects in disk formation from observational perspective. We have analyzed the data from the polarization and molecular-line surveys of star-forming regions. Based on theoretical predictions, to explain the probability distributions of the misalignment angles and numbers of disks from observations, misalignment is unlikely to be a dominant mechanism in disk formation, and other mechanisms should take place. Nevertheless, we indeed found a correlation between the gas kinematics and misalignment angles, suggesting that misalignment likely prompts the angular momentum transportation from large to small scale in protostellar sources. By further investigating the magnetic field strength on the scales of dense cores (0.1 pc) and protostellar envelopes (1000 au) around a young protostar, our result suggests increasing mass-to-flux ratios from the large to small scales and hints that the magnetic field is partially decoupled from neutral matter. This result could support the scenario of efficient non-ideal MHD effects, in particular ambipolar diffusion, prompt the formation of the 20 au disk around this young protostar.