On the fragmentation boundary in magnetised self-gravitating discs

Abstract

We investigate the role of magnetic fields in the fragmentation of self-gravitating discs using 3D global ideal magnetohydrodynamic simulations performed with the "phantom" smoothed particle hydrodynamics code. For initially toroidal fields, we find two regimes. In the first, where the cooling time is greater than five times the dynamical time, magnetic fields reduce spiral density wave amplitudes, which in turn suppresses fragmentation. This is the case even if the magnetic pressure is only a tenth of the thermal pressure. The second regime occurs when the cooling time is sufficiently short that magnetic fields cannot halt fragmentation. We find that magnetised discs produce more massive fragments, due to both the additional pressure exerted by the magnetic field, and the additional angular momentum transport induced by Maxwell stresses. The fragments are confined to a narrower range of initial semimajor axes than those in unmagnetised discs. The orbital eccentricity and inclination distributions of unmagnetised and magnetised disc fragments are similar. Our results suggest the fragmentation boundary could be at cooling times a factor of two lower than predicted by purely hydrodynamical models.

12 pages, 22 figures, accepted for publication in MNRAS

References in corpus (12)

• SPLASH: An interactive visualisation tool for Smoothed Particle Hydrodynamics simulations
• Smoothed Particle Hydrodynamics and Magnetohydrodynamics
• The impact of magnetic fields on single and binary star formation
• A Triple Protostar System Formed via Fragmentation of a Gravitationally Unstable Disk
• Characterising the Gravitational Instability in Cooling Accretion Discs
• Radiation Magnetohydrodynamic Simulations of Protostellar Collapse: Non-Ideal Magnetohydrodynamic Effects and Early Formation of Circumstellar Disks
• Constrained Hyperbolic Divergence Cleaning for Smoothed Particle Magnetohydrodynamics
• A Sub-arcsecond Survey Toward Class 0 Protostars in Perseus: Searching for Signatures of Protostellar Disks
• On the gap-opening criterion of migrating planets in protoplanetary disks
• Effects of radiation transfer on the structure of self-gravitating disks, their fragmentation and evolution of the fragments
• Constrained hyperbolic divergence cleaning in smoothed particle magnetohydrodynamics with variable cleaning speeds
• Linear stability of magnetized massive protoplanetary disks

Cited by in corpus (9)

• The fragmentation criteria in local vertically stratified self-gravitating disk simulations
• 13C17O suggests gravitational instability in the HL Tau disc
• Disc formation and fragmentation using radiative non-ideal magnetohydrodynamics
• Formation of intermediate-mass planets via magnetically-controlled disk fragmentation
• Magnetorotational instability and dynamo action in gravitoturbulent astrophysical discs
• Local simulations of MRI turbulence with meshless methods
• Filling in the Gaps: Can Gravitationally Unstable Discs Form the Seeds of Gas Giant Planets?
• The 3D structure of disc-instability protoplanets
• Gravitoturbulent dynamo in global simulations of gaseous disks