Disk formation during collapse of magnetized protostellar cores

P. Hennebelle; A. Ciardi

doi:10.1051/0004-6361/200913008

paper

Disk formation during collapse of magnetized protostellar cores

arXiv:0909.3190 · doi:10.1051/0004-6361/200913008

Abstract

In the context of star and planet formation, understanding the formation of disks is of fundamental importance. Previous studies found that the magnetic field has a very strong impact on the collapse of a prestellar cloud, particularly in possibly suppressing the formation of a disk even for relatively modest values of the magnetic intensity. Since observations infer that cores have a substantial level of magnetization, this raises the question of how disks form. However, most studies have been restricted to the case in which the initial angle, $α$ , between the magnetic field and the rotation axis equals 0 $^{\circ}$ . We explore and analyse the influence of non aligned configurations on disk formation. We perform 3D ideal MHD, AMR numerical simulations for various values of $μ$ , the ratio of the mass-to-flux to the critical mass-to-flux, and various values of $α$ . We find that disks form more easily as $α$ increases from 0 to 90 $^{\circ}$ . We propose that as the magnetized pseudo-disks become thicker with increasing $α$ , the magnetic braking efficiency is lowered. We also find that even small values of $α$ ( $≃$ 10-20 $^{\circ}$ ) show significant differences with the alligned case. Within the framework of ideal MHD and for our choice of initial conditions, centrifugally supported disks cannot form for values of $μ$ smaller than $≃$ 3, if the magnetic field and the rotation axis are perpendicular, and smaller than about $≃$ 5-10 when they are perfectly aligned.

accepted for publication in A&A

Disk formation during collapse of magnetized protostellar cores

Abstract

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