The role of magnetic field and stellar feedback in the evolution of filamentary structures in collapsing star-forming clouds

¹ Aix Marseille Univ, CNRS, CNES, LAM Marseille, France
² Institute for Advanced Study, Kyushu University, Japan
³ Department of Earth and Planetary Sciences, Faculty of Science, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
⁴ Division of Science, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
⁵ Institut Universitaire de France, 1 rue Descartes, 75005 Paris, France
⁶ AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France

^★ Corresponding author: paolo.suin@lam.fr

Received: 17 January 2025
Accepted: 24 April 2025

Abstract

Context. Filaments are common features in molecular clouds and they play a key role in star formation. Studying their life cycle is essential to fully understand the star formation process.

Aims. Using high-resolution magnetohydrodynamical simulations including early stellar feedback (jets and H II regions), we aim to characterise the impact of magnetic field (B) and stellar feedback on the evolution of filamentary structures in star-forming clouds.

Methods. We performed two numerical simulations of a collapsing 10⁴ M_⊙ cloud with different mass-to-flux ratios (μ = 2 and μ = 8). Using DisPerSE, we extracted the three-dimensional filamentary network and analysed its morphological and physical properties as it evolves throughout the star formation event.

Results. We find that the B plays a central role in shaping the density structures as the clouds evolve. With a weak field, the cloud develops a single central hub, while in strong B fields the cloud maintains a sparser filamentary network. A stronger magnetisation also delays star formation, although the two runs ultimately achieved similar star formation efficiencies. We observed that the filaments in the simulations follow two distinct evolutionary pathways. In the strongly magnetised case, filaments are predominantly perpendicular to B lines, favouring a parallel alignment in the weak field cloud. Furthermore, while always accreting, filaments exhibit faster flows towards the hub relative to the surrounding gas. In the weakly magnetised run, the central hub dominates the dynamics, and filaments exhibit faster flows as they approach the central hub. Finally, once the expanding H II region impacts the filaments, they align to B independently of the initial configuration.

Conclusions. Magnetic fields play a critical role in shaping the structure and dynamics of molecular clouds. Stronger magnetic fields slow the cloud’s evolution and inhibit the formation of central hubs, promoting a broader filamentary network instead. However, ionising feedback dominates the late-stage evolution, overriding the initial differences and dictating the final filament configuration.