Non-ideal magnetohydrodynamics vs turbulence II: Which is the dominant process in stellar core 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 protostars by following the gravitational collapse of 1~M${}_{\odot }$ gas clouds through the first hydrostatic core to stellar densities. The clouds are imposed with both rotational and turbulent velocities, and are threaded with a magnetic field that is parallel/anti-parallel or perpendicular to the rotation axis; we investigate two rotation rates and four Mach numbers. The initial radius and mass of the stellar core are only weakly dependent on the initial parameters. In the models that include ideal MHD, the magnetic field strength implanted in the protostar at birth is much higher than observed, independent of the initial level of turbulence; only non-ideal MHD can reduce this strength to near or below the observed levels. This suggests that not only is ideal MHD an incomplete picture of star formation, but that the magnetic fields in low mass stars are implanted later in life by a dynamo process. Non-ideal MHD suppresses magnetically launched stellar core outflows, but turbulence permits thermally launched outflows to form a few years after stellar core formation.

Accepted for publication in MNRAS. 12 pages, 9 figures

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Cited by in corpus (8)

• Collapse of turbulent massive cores with ambipolar diffusion and hybrid radiative transfer I. Accretion and multiplicity
• Non-ideal magnetohydrodynamics vs turbulence I: Which is the dominant process in protostellar disc formation?
• The impact of non-ideal magnetohydrodynamic processes on discs, outflows, counter-rotation and magnetic walls during the early stages of star 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
• The initial magnetic criticality of prestellar cores
• Star-forming environments in smoothed particle magnetohydrodynamics simulations I: Clump extraction and properties
• The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars VI. Insights from Radiative Transfer Modeling