CMR exploration I -- filament structure with synthetic observations

TL;DR

This study investigates how varying physical conditions affect filament formation via collision-induced magnetic reconnection (CMR) in molecular clouds, revealing chaotic filament structures and temporary magnetic-density relations.

Contribution

It performs a comprehensive parameter exploration of the CMR mechanism using resistive MHD simulations, highlighting the impact of seven physical parameters on filament morphology and structure.

Findings

Filaments exhibit rich, variable sub-structures.

Magnetic field and density show a temporary proportionality.

Filament morphology is highly sensitive to initial conditions.

Abstract

In this paper, we carry out a pilot parameter exploration for the collision-induced magnetic reconnection (CMR) mechanism that forms filamentary molecular clouds. Following Kong et al. (2021), we utilize Athena++ to model CMR in the context of resistive magnetohydrodynamics (MHD), considering the effect from seven physical conditions, including the Ohmic resistivity ($\eta$), the magnetic field ($B$), the cloud density ($\rho$), the cloud radius $R$, the isothermal temperature $T$, the collision velocity $v_x$, and the shear velocity $v_z$. Compared to their fiducial model, we consider a higher and a lower value for each one of the seven parameters. We quantify the exploration results with five metrics, including the density probability distribution function ($\rho$-PDF), the filament morphology (250 $\mu$m dust emission), the $B$-$\rho$ relation, the dominant fiber width, and the ringiness that describes the significance of the ring-like sub-structures. The exploration forms straight and curved CMR-filaments with rich sub-structures that are highly variable in space and time. The variation translates to fluctuation in all the five metrics, reflecting the chaotic nature of magnetic reconnection in CMR. A temporary $B\propto\rho$ relation is noticeable during the first 0.6 Myr. Overall, the exploration provides useful initial insights to the CMR mechanism.