Impact of Turbulent Magnetic Fields on Disk Formation and Fragmentation in First Star Formation

TL;DR

This study uses 3D magnetohydrodynamics simulations to show that turbulent magnetic fields can significantly influence disk formation, fragmentation, and the initial mass function of the first stars in the early universe.

Contribution

It demonstrates that strong turbulent magnetic fields can stabilize disks and reduce fragmentation, highlighting their crucial role in first star formation, which was previously underestimated.

Findings

Magnetic pressure and torques stabilize disks and reduce fragmentation.

Magnetic fields can launch protostellar jets, but with minor impact.

Magnetic effects likely influence the initial mass function of first stars.

Abstract

Recent cosmological hydrodynamic simulations have suggested that the first stars in the universe often form as binary or multiple systems. However, previous studies typically overlooked the potential influence of magnetic fields during this process, assuming them to be weak and minimally impactful. Emerging theoretical investigations, however, propose an alternative perspective, suggesting that turbulent dynamo effects within first-star forming clouds can generate strong magnetic fields. In this study, we perform three-dimensional ideal magnetohydrodynamics simulations, starting from the gravitational collapse of a turbulent cloud core to the early accretion phase, where disk fragmentation frequently occurs. Our findings reveal that turbulent magnetic fields, if they reach an equipartition level with turbulence energy across all scales during the collapse phase, can significantly affect the properties of the multiple systems. Specifically, both magnetic pressure and torques contribute to disk stabilization, leading to a reduction in the number of fragments, particularly for low-mass stars. Additionally, our observations indicate the launching of protostellar jets driven by magnetic pressure of toroidal fields, although their overall impact on star formation dynamics appears to be minor. Given the case with which seed magnetic fields amplify to the full equipartition level, our results suggest that magnetic fields likely play a significant role in shaping the initial mass function of the first stars, highlighting the importance of magnetic effects on star formation in the early universe.