Non-ideal magnetohydrodynamics versus turbulence II : which is the dominant process in stellar core formation?
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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☉ 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/antiparallel 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.
Wurster , J H & Lewis , B T 2020 , ' Non-ideal magnetohydrodynamics versus turbulence II : which is the dominant process in stellar core formation? ' , Monthly Notices of the Royal Astronomical Society , vol. 495 , no. 4 , pp. 3807-3818 . https://doi.org/10.1093/mnras/staa1340
Monthly Notices of the Royal Astronomical Society
Copyright © 2020 the Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the final published version of the work, which was originally published at https://doi.org/10.1093/mnras/staa1340.
DescriptionFunding: JW acknowledges support from the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007- 2013 grant agreement no. 339248), and from the University of St Andrews. BTL acknowledges the support of the National Aeronautics and Space Administration (NASA) through grant NN17AK90G and from the National Science Foundation (NSF) through grants no. 1517488 and PHY-1748958.
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