Misalignment of Magnetic Fields, Outflows and Discs in Star-forming Clouds

TL;DR

This study uses resistive magnetohydrodynamics simulations to explore how magnetic fields, outflows, and discs in star-forming clouds are misaligned, revealing that their orientations are generally uncorrelated during early star formation.

Contribution

It demonstrates through simulations that the directions of jets, discs, and magnetic fields are typically misaligned and change over time, challenging the interpretation of observational data.

Findings

Jet properties are similar across different initial misalignment angles.

Jet, disc, and magnetic field directions are usually not aligned and vary over time.

Observations of these directions at small scales cannot reliably inform star formation processes.

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 prestellar cloud phase until $\sim$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 $\theta_0$. We calculate the cloud evolution for nine models with different $\theta_0 (=$ 0, 5, 10, 30, 45, 60, 80, 85, 90$^\circ$). 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 $\theta_0=90^\circ$. 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 $\theta_0=0^\circ$. Even when the rotation axis of the prestellar 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 $\lesssim 1000$ au. Thus, we cannot use such observations to derive any restrictions on the star formation process.