D. Seifried, R. Banerjee, R. E. Pudritz, R. S. Klessen
We present collapse simulations of 100 M_{\sun}, turbulent cloud cores
threaded by a strong magnetic field. During the initial collapse phase
filaments are generated which fragment quickly and form several protostars.
Around these protostars Keplerian discs with typical sizes of a few 10 AU build
up in contrast to previous simulations neglecting turbulence. We examine three
mechanisms potentially responsible for lowering the magnetic braking efficiency
and therefore allowing for the formation of Keplerian discs. Analysing the
condensations in which the discs form, we show that the build-up of Keplerian
discs is neither caused by magnetic flux loss due to turbulent reconnection nor
by the misalignment of the magnetic field and the angular momentum. It is
rather a consequence of the turbulent surroundings of the disc which exhibit no
coherent rotation structure while strong local shear flows carry large amounts
of angular momentum. We suggest that the "magnetic braking catastrophe", i.e.
the formation of sub-Keplerian discs only, is an artefact of the idealised
non-turbulent initial conditions and that turbulence provides a natural
mechanism to circumvent this problem.
View original:
http://arxiv.org/abs/1201.5302
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