The impact of non-ideal magnetohydrodynamics on binary star formation
Monthly Notices of the Royal Astronomical Society
Oxford University Press (OUP) for Royal Astronomical Society
© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
We investigate the effect of non-ideal magnetohydrodynamics (MHD) on the formation of binary stars using a suite of three-dimensional smoothed particle magnetohydrodynamics simulations of the gravitational collapse of 1 M⊙, rotating, perturbed molecular-cloud cores. Alongside the role of Ohmic resistivity, ambipolar diffusion and the Hall effect, we also examine the effects of magnetic field strength, orientation and amplitude of the density per- turbation. When modelling sub-critical cores, ideal MHD models do not collapse whereas non-ideal MHD models collapse to form single protostars. In supercritical ideal MHD models, increasing the magnetic field strength or decreasing the initial-density perturbation amplitude decreases the initial binary separation. Strong magnetic fields initially perpendicular to the rotation axis suppress the formation of binaries and yield discs with magnetic fields ∼10 times stronger than if the magnetic field was initially aligned with the rotation axis. When non-ideal MHD is included, the resulting discs are larger and more massive, and the binary forms on a wider orbit. Small differences in the supercritical cores caused by non-ideal MHD effects are amplified by the binary interaction near periastron. Overall, the non-ideal effects have only a small impact on binary formation and early evolution, with the initial conditions playing the dominant role.
JW and MRB acknowledge support from the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007–2013 grant agreement no. 339248). JW also acknowledges support from the Australian Research Council (ARC) Discovery Projects Grant DP130102078. DJP is funded by ARC Future Fellowship FT130100034. This work was supported by resources on the gSTAR national facility at Swinburne University of Technology and by Zen. gSTAR is funded by Swinburne and the Australian Government’s Education Investment Fund. Several calculations for this paper were performed on the University of Exeter Supercomputer, a DiRAC Facility jointly funded by STFC, the Large Facilities Capital Fund of BIS, and the University of Exeter.
This is the final version of the article. Available from the publisher via the DOI in this record.
Vol. 466, 1788–1804