Evolution of Magnetic Fields in Collapsing Star-forming Clouds under Different Environments

TL;DR

This study uses magnetohydrodynamics simulations to explore how magnetic fields evolve and dissipate in star-forming clouds across different galactic environments, considering factors like metallicity and ionization.

Contribution

It provides a comprehensive analysis of magnetic field dissipation processes in star-forming clouds under diverse environmental conditions, including primordial and non-primordial scenarios.

Findings

Magnetic field dissipation varies with environment and ionization levels.

Dominant dissipation processes depend on environmental factors.

Primordial clouds rarely dissipate magnetic fields without ionization sources.

Abstract

In nearby star-forming clouds, amplification and dissipation of the magnetic field are known to play crucial roles in the star-formation process. The star-forming environment varies from place to place and era to era in galaxies. In the present study, amplification and dissipation of magnetic fields in star-forming clouds are investigated under different environments using magnetohydrodynamics (MHD) simulations. We consider various star-forming environments in combination with the metallicity and the ionization strength, and prepare prestellar clouds having two different mass-to-flux ratios. We calculate the cloud collapse until protostar formation using ideal and non-ideal (inclusion and exclusion of Ohmic dissipation and ambipolar diffusion) MHD calculations to investigate the evolution of the magnetic field. We perform 288 runs in total and show the diversity of the density range within which the magnetic field effectively dissipates, depending on the environment. In addition, the dominant dissipation process (Ohmic dissipation or ambipolar diffusion) is shown to strongly depend on the star-forming environment. Especially, for the primordial case, magnetic field rarely dissipates without ionization source, while it efficiently dissipates when very weak ionization sources exist in the surrounding environment. The results of the present study help to clarify star formation in various environments.