The properties of clusters, and the orientation of magnetic fields relative to filaments, in magnetohydrodynamic simulations of colliding clouds

C L Dobbs,J Wurster

doi:10.1093/mnras/stab150

Abstract

ABSTRACT We have performed Smoothed Particle Magneto-Hydrodynamics (SPMHD) calculations of colliding clouds to investigate the formation of massive stellar clusters, adopting a timestep criterion to prevent large divergence errors. We find that magnetic fields do not impede the formation of young massive clusters (YMCs), and the development of high star formation rates, although we do see a strong dependence of our results on the direction of the magnetic field. If the field is initially perpendicular to the collision, and sufficiently strong, we find that star formation is delayed, and the morphology of the resulting clusters is significantly altered. We relate this to the large amplification of the field with this initial orientation. We also see that filaments formed with this configuration are less dense. When the field is parallel to the collision, there is much less amplification of the field, dense filaments form, and the formation of clusters is similar to the purely hydrodynamical case. Our simulations reproduce the observed tendency for magnetic fields to be aligned perpendicularly to dense filaments, and parallel to low density filaments. Overall our results are in broad agreement with past work in this area using grid codes.

Highlights

D Recent works have shown that young massive clouds E (YMCs) can form through the collision of molecular clouds N (Dobbs et al 2020; Liow & Dobbs 2020)
ITare initially allocated on a grid in both the clouds and the with magnetic fields, though our focus is on the formation of massive clusters rather than individual stars
We have performed Smoothed Particle Magneto-Hydrodynamics (SPMHD) simulations of colliding clouds with magnetic fields to investigate the formation of massive clusters

Summary

INTRODUCTION

D Recent works have shown that young massive clouds E (YMCs) can form through the collision of molecular clouds N (Dobbs et al 2020; Liow & Dobbs 2020). These previous simulations are all purely hydrodynamical Whether such clusters still form when magnetic fields are present, and still have the same properties, is an open question. Liow & Dobbs (2020) carried out a paI rameter study showing high density, low turbulence and high velocities promote YMC formation. ITare initially allocated on a grid in both the clouds and the with magnetic fields, though our focus is on the formation of massive clusters rather than individual stars. As for the previous simulations (Liow & Dobbs 2020), we apply a turbulent velocity field to each cloud.

Details of Simulations

RESULTS

Star formation rates

Magnetic field and filaments

CONCLUSIONS