Formation of dust filaments in the diffuse envelopes of molecular clouds

TL;DR

This paper introduces a new charged dust particle module to study dust dynamics in molecular cloud envelopes, revealing how magnetic coupling causes dust structures to form independently of gas, impacting star formation models.

Contribution

The study presents a novel charged dust particle module and demonstrates its role in forming decoupled dust filaments in turbulent, magnetized molecular cloud envelopes.

Findings

Charged dust grains form elongated structures decoupled from gas.

Magnetic coupling influences dust-to-gas ratio variations.

Dust dynamics are crucial for accurate star formation simulations.

Abstract

The path to understanding star formation processes begins with the study of the formation of molecular clouds. The outskirts of these clouds are characterized by low column densities that allow the penetration of ultraviolet radiation, resulting in a non-negligible ionization fraction and the charging of the small dust grains that are mixed with the gas; this diffuse phase is then coupled to the ambient magnetic field. Despite the general assumption that dust and gas are tightly correlated, several observational and theoretical studies have reported variations in the dust-to-gas ratio toward diffuse and cold clouds. In this work, we present the implementation of a new charged particles module for analyzing the dust dynamics in molecular cloud envelopes. We study the evolution of a single population of small charged grains (0.05 $\mu$m) in the turbulent, magnetized molecular cloud envelope using this module. We show that variations in the dust-to-gas ratio arise due to the coupling of the grains with the magnetic field, forming elongated dust structures decoupled from the gas. This emphasizes the importance of considering the dynamics of charged dust when simulating the different phases of the interstellar medium, especially for star formation studies.