Misalignment of magnetic fields, outflows, and discs in star-forming clouds. Issue 2 (15th November 2019)

• Record Type: Journal Article
• Authors: Machida, Masahiro N; Hirano, Shingo; Kitta, Hideyuki
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 491:Issue 2(2020)
• Page Start: 2180
• Page End: 2197
• Publication Date: 2019-11-15
• Subjects: MHD -- stars: formation -- stars: magnetic field -- stars: protostars -- stars: winds, outflows; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz3159
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Using resistive magnetohydrodynamics simulations, the propagation of protostellar jets, the formation of circumstellar discs, and the configuration of magnetic fields are investigated from the pre-stellar cloud phase until ∼500 yr after protostar formation. As the initial state, we prepare magnetized rotating clouds, in which the rotation axis is misaligned with the global magnetic field by an angle θ0 . We calculate the cloud evolution for nine models with different θ0 (= 0°, 5°, 10°, 30°, 45°, 60°, 80°, 85°, 90°). Our simulations show that there is no significant difference in the physical quantities of the protostellar jet, such as the mass and momentum, among the models except for the model with θ0 = 90°. On the other hand, the directions of the jet, disc normal, and magnetic field are never aligned with each other during the early phase of star formation except for the model with θ0 = 0°. Even when the rotation axis of the pre-stellar cloud is slightly inclined to the global magnetic field, the directions of the jet, disc normal, and local magnetic field differ considerably, and they randomly change over time. Our results indicate that it is very difficult to extract any information from the observations of the directions of the outflow, disc, and magnetic field at the scale of ≲1000 au. Thus, we cannot use such observations to derive any restrictions on the star formation process.