The effect of magnetic fields on star cluster formation

TL;DR

This study uses simulations to explore how magnetic fields influence star cluster formation, revealing that stronger magnetic fields significantly alter cloud structures, suppress star formation, and affect the types of stars formed.

Contribution

It provides new insights into the role of magnetic fields in star formation, especially how they create large-scale structures and reduce star formation efficiency in molecular clouds.

Findings

Magnetic fields create large-scale voids in molecular clouds.

Strong magnetic fields reduce star formation by up to 75%.

Magnetic fields influence the formation of brown dwarfs.

Abstract

We examine the effect of magnetic fields on star cluster formation by performing simulations following the self-gravitating collapse of a turbulent molecular cloud to form stars in ideal MHD. The collapse of the cloud is computed for global mass-to-flux ratios of infinity, 20, 10, 5 and 3, that is using both weak and strong magnetic fields. Whilst even at very low strengths the magnetic field is able to significantly influence the star formation process, for magnetic fields with plasma beta < 1 the results are substantially different to the hydrodynamic case. In these cases we find large-scale magnetically-supported voids imprinted in the cloud structure; anisotropic turbulent motions and column density structure aligned with the magnetic field lines, both of which have recently been observed in the Taurus molecular cloud. We also find strongly suppressed accretion in the magnetised runs, leading to up to a 75% reduction in the amount of mass converted into stars over the course of the calculations and a more quiescent mode of star formation. There is also some indication that the relative formation efficiency of brown dwarfs is lower in the strongly magnetised runs due to the reduction in the importance of protostellar ejections.