Impact Of Magnetic Fields On Molecular Cloud Formation & Evolution

TL;DR

This study uses magnetohydrodynamical simulations to explore how magnetic fields influence molecular cloud formation and star formation, revealing that strong magnetic fields delay or prevent star formation despite core formation.

Contribution

It demonstrates that magnetic field strength and flow orientation critically affect star formation, highlighting the persistent challenge of forming supercritical cloud cores.

Findings

Dense cores form under all conditions.

Star formation is delayed or suppressed with magnetic fields >3 microGauss.

Inclined flows do not produce supercritical cores.

Abstract

We use magnetohydrodynamical simulations of converging flows to investigate the process of molecular cloud formation and evolution out of the magnetised ISM. Here, we investigate whether the observed subcritical HI clouds can become supercritical and hence allow the formation of stars within them. To do so, we vary the turbulent Mach number of the flows, as well as the initial magnetic field strength. We show that dense cores are able to build up under all conditions, but that star formation in these cores is either heavily delayed or completely suppressed if the initial field strength is B>3 microGauss. To probe the effect of magnetic diffusion, we introduce a tilting angle between the flows and the uniform background magnetic field, which mimics non--ideal MHD effects. Even with highly inclined flows, the formed cores are devoid of star formation, because no magnetically supercritical regions are build up. Hence we conclude, that the problem of how supercritical cloud cores are generated still persists.