Growth of Massive Molecular Cloud Filament by Accretion Flows. II. New Mechanism to Support a Supercritical Filament against Radial Collapse

TL;DR

This paper introduces the STORM mechanism, where ambipolar diffusion-driven turbulence at accretion shocks sustains the width of supercritical molecular filaments, preventing their radial collapse and influencing star formation.

Contribution

It proposes a new magnetic diffusion-based mechanism (STORM) that maintains filament width against collapse, supported by non-ideal MHD simulations.

Findings

STORM mechanism sustains filament width at high line masses.

Ambipolar diffusion enables gas flow across magnetic fields at shocks.

Turbulence driven by blobs influences filament stability.

Abstract

Observations indicate that dense molecular filamentary clouds are sites of star formation. The filament width determines the most unstable scale for self-gravitational fragmentation and influences the stellar mass. Therefore, constraining the evolution of filaments and the origin of their properties are important for understanding star formation. Although some observations show a universal width of 0.1 pc, many theoretical studies predict the contraction of thermally supercritical filaments (> 17 Msun pc-1) due to radial collapse. Through non-ideal magnetohydrodynamics simulations with ambipolar diffusion, we explore the formation and evolution of filaments via slow-shock instability at the front of accretion flows. We reveal that ambipolar diffusion allows the gas in the filament to flow across the magnetic fields around the shock front, forming dense blobs behind the concave points of the shock front. The blobs transfer momentum that drives internal turbulence. We name this mechanism the "STORM" (Slow-shock-mediated Turbulent flOw Reinforced by Magnetic diffusion). The persistence and efficiency of the turbulence inside the filament are driven by the magnetic field and the ambipolar diffusion effect, respectively. The STORM mechanism sustains the width even when the filament reaches very large line masses (~ 100 Msun pc-1).