Collapse of a molecular cloud core to stellar densities: stellar-core and outflow formation in radiation magnetohydrodynamic simulations
Bate, Matthew R.
Tricco, Terrence S.
Price, Daniel J.
Monthly Notices of the Royal Astronomical Society
Oxford University Press
We have performed smoothed particle radiation magnetohydrodynamic simulations of the collapse of rotating, magnetized molecular cloud cores to form protostars. The calculations follow the formation and evolution of the first hydrostatic core, the collapse to form a stellar core, the launching of outflows from both the first hydrostatic core and stellar core, and the breakout of the stellar outflow from the remnant of the first core. We investigate the roles of magnetic fields and thermal feedback on the outflow launching process, finding that both magnetic and thermal forces contribute to the launching of the stellar outflow. We also follow the stellar cores until they grow to masses of up to 20 Jupiter-masses, and determine their properties. We find that at this early stage, before fusion begins, the stellar cores have radii of ≈3 R⊙ with radial entropy profiles that increase outward (i.e. are convectively stable) and minimum entropies per baryon of s/kB ≈ 14 in their interiors. The structure of the stellar cores is found to be insensitive to variations in the initial magnetic field strength. With reasonably strong initial magnetic fields, accretion on to the stellar cores occurs through inspiralling magnetized pseudo-discs with negligible radiative losses, as opposed to first cores which effectively radiate away the energy liberated in the accretion shocks at their surfaces. We find that magnetic field strengths of >10 kG can be implanted in stellar cores at birth.
University of Exeter Visiting International Academic Fellowship
Australian Research Council Discovery Project Grant
Endeavour IPRS and APA postgraduate research scholarships
University of Exeter Supercomputer: jointly funded by Science and Technology Facilities Council (STFC), Large Facilities Capital Fund of BIS, and the University of Exeter
DiRac Complexity computer: jointly funded by Science and Technology Facilities Council (STFC) and the Large Facilities Capital Fund of BIS
The dataset used to produce this paper can be accessed at http://hdl.handle.net/10871/13883
This article has been accepted for publication in MNRAS ©: 2013 Bate et al. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Vol. 437, Issue 1, pp. 77 - 95