The Origin of Filamentary Star Forming Clouds in Magnetised Galaxies

TL;DR

This study uses global numerical simulations to show that magnetic buoyancy via Parker instability creates giant filaments in galactic discs, which then fragment into star-forming clouds, explaining the transition from magnetically supported to star-forming regions.

Contribution

The paper demonstrates how magnetic buoyancy and Parker instability lead to filament formation and cloud collapse in magnetised galactic discs, providing a new understanding of star formation initiation.

Findings

Magnetic buoyancy causes giant filament formation in galactic discs.

Filaments become gravitationally unstable and fragment into massive clouds.

The process explains the transition from magnetically subcritical to supercritical regions.

Abstract

Observations show that galaxies and their interstellar media are pervaded by strong magnetic fields with energies in the diffuse component being at least comparable to the thermal and even as large or larger than the turbulent energy. Such strong magnetic fields prevent the formation of stars because patches of the interstellar medium are magnetically subcritical. Here we present the results from global numerical simulations of strongly magnetised and self-gravitating galactic discs, which show that the buoyancy of the magnetic field due to the Parker instability leads at first to the formation of giant filamentary regions. These filamentary structures become gravitationally unstable and fragment into $\sim10^5 M_{\odot}$ clouds that attract kpc long, coherent filamentary flows that build them into GMCs. Our results thus provide a solution to the long-standing problem of how the transition from sub- to supercritical regions in the interstellar medium proceeds.