Collapse, outflows and fragmentation of massive, turbulent and
  magnetized prestellar barotropic cores
  Stars and more particularly massive stars, have a drastic impact on galaxy
evolution. Yet the conditions in which they form and collapse are still not
fully understood. In particular, the influence of the magnetic field on the
collapse of massive clumps is relatively unexplored, it is thus of great
relevance in the context of the formation of massive stars to investigate its
impact. We perform high resolution, MHD simulations of the collapse of hundred
solar masses, turbulent and magnetized clouds, using the adaptive mesh
refinement code RAMSES. We compute various quantities such as mass
distribution, magnetic field and angular momentum within the collapsing core
and study the episodic outflows and the fragmentation that occurs during the
collapse. The magnetic field has a drastic impact on the cloud evolution. We
find that magnetic braking is able to substantially reduce the angular momentum
in the inner part of the collapsing cloud. Fast and episodic outflows are being
launched with typical velocities of the order of 3-5 km s$^{-1}$ although the
highest velocities can be as high as 30-40 km s$^{-1}$. The fragmentation in
several objects, is reduced in substantially magnetized clouds with respect to
hydrodynamical ones by a factor of the order of 1.5-2. We conclude that
magnetic fields have a significant impact on the evolution of massive clumps.
In combination with radiation, magnetic fields largely determine the outcome of
massive core collapse. We stress that numerical convergence of MHD collapse is
a challenging issue. In particular, numerical diffusion appears to be important
at high density therefore possibly leading to an over-estimation of the number
of fragments.
