The impact of non-ideal magnetohydrodynamics on binary star formation

TL;DR

This study explores how non-ideal magnetohydrodynamics influences binary star formation, revealing that while initial conditions are dominant, non-ideal effects subtly alter disc size, mass, and binary separation.

Contribution

It provides the first detailed analysis of non-ideal MHD effects on binary star formation using 3D simulations, highlighting their subtle influence compared to initial conditions.

Findings

Non-ideal MHD enables collapse of sub-critical cores into single protostars.

Magnetic field orientation affects binary formation and disc properties.

Initial conditions have a greater impact than non-ideal MHD effects.

Abstract

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 one solar mass, 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 perturbation. When modelling sub-critical cores, ideal MHD models do not collapse whereas non-ideal MHD models collapse to form single protostars. In super-critical 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 super-critical 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.