Non-ideal magnetohydrodynamics vs turbulence I: Which is the dominant process in protostellar disc formation?

Abstract

Non-ideal magnetohydrodynamics (MHD) is the dominant process. We investigate the effect of magnetic fields (ideal and non-ideal) and turbulence (sub- and transsonic) on the formation of circumstellar discs that form nearly simultaneously with the formation of the protostar. This is done by modelling the gravitational collapse of a 1~M${}_{\odot }$ gas cloud that is threaded with a magnetic field and imposed with both rotational and turbulent velocities. We investigate magnetic fields that are parallel/anti-parallel and perpendicular to the rotation axis, two rotation rates and four Mach numbers. Disc formation occurs preferentially in the models that include non-ideal MHD where the magnetic field is anti-parallel or perpendicular to the rotation axis. This is independent of the initial rotation rate and level of turbulence, suggesting that subsonic turbulence plays a minimal role in influencing the formation of discs. Aside from first core outflows which are influenced by the initial level of turbulence, non-ideal MHD processes are more important than turbulent processes during the formation of discs around low-mass stars.

Accepted for publication in MNRAS. 12 pages, 8 figures

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• Non-ideal magnetohydrodynamics vs turbulence II: Which is the dominant process in stellar core formation?
• Do we need non-ideal magnetohydrodynamics to model protostellar discs?
• On the origin of magnetic fields in stars II: The effect of numerical resolution
• No impact of core-scale magnetic field, turbulence, or velocity gradient on sizes of protostellar disks in Orion A
• The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars VI. Insights from Radiative Transfer Modeling