Marc Joos, Patrick Hennebelle, Andrea Ciardi
Theoretical studies of collapsing clouds found that the presence of a relatively strong magnetic field may prevent the formation of disks and their fragmentation. However most previous studies have been limited to cases where the magnetic field and the rotation axis of the cloud are aligned. We study the transport of angular momentum, and the effects on disk formation, for non-aligned initial configurations, and for a range magnetic intensities. We perform three-dimensional, adaptive mesh, numerical simulations of magnetically supercritical collapsing dense cores using the magneto-hydrodynamic code Ramses. At variance to earlier analysis, we show that the transport of angular momentum acts less efficiently in collapsing cores with non-aligned rotation and magnetic field. Analytically this result can be understood by taking into account the bending of field lines occurring during the gravitational collapse. We find that massive disks, containing at least 10% of the intial core mass, can form during the earliest stages of star formation even for mass-to-flux ratios as low as 3 to 5 times the critical value. At higher field intensities, the early formation of massive disks is prevented. Given the ubiquity of Class I disks, and that the early formation of massive disks can take place at moderate magnetic intensities, we speculate that for stronger fields disks will form later, when most of the envelope will have been accreted. In addition, we speculate that some observed early massive disks may actually be outflows cavity, mistaken for disks by projection effects.
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http://arxiv.org/abs/1203.1193
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