Implementation of dust particles in three-dimensional magnetohydrodynamics simulation: Dust dynamics in a collapsing cloud core

TL;DR

This study models dust dynamics in star-forming clouds using a novel Lagrangian approach combined with magnetohydrodynamics, revealing size-dependent dust-gas coupling and concentration effects during collapse.

Contribution

It introduces a new method for calculating dust trajectories as Lagrangian particles in 3D MHD simulations, enhancing understanding of dust behavior in star formation.

Findings

Dust grains ≤ 10 μm are well coupled with gas.

Large dust grains (> 100 μm) concentrate faster in the central region.

The Lagrangian dust trajectory method reproduces previous Eulerian results.

Abstract

The aim of this study is to examine dust dynamics on a large scale and investigate the coupling of dust with gas fluid in the star formation process. We propose a method for calculating the dust trajectory in a gravitationally collapsing cloud, where the dust grains are treated as Lagrangian particles and are assumed to be neutral. We perform the dust trajectory calculations in combination with non-ideal magnetohydrodynamics simulation. Our simulation shows that dust particles with a size of $\le 10\,{\rm \mu m}$ are coupled with gas in a star-forming cloud core. We investigate the time evolution of the dust-to-gas mass ratio and the Stokes number, which is defined as the stopping time normalized by the freefall time-scale, and show that large dust grains ($\gtrsim 100\,{\rm \mu m}$) have a large Stokes number (close to unity) and tend to concentrate in the central region (i.e., protostar and rotationally supported disk) faster than do small grains ($\lesssim 10\,{\rm \mu m}$). Thus, large grains significantly increase the dust-to-gas mass ratio around and inside the disk. We also confirm that the dust trajectory calculations, which trace the physical quantities of each dust particle, reproduce previously reported results obtained using the Eulerian approach.