  Like their lower mass siblings, massive protostars can be expected to: a) be
surrounded by circumstellar disks and b) launch magnetically-driven jets and
outflows. The disk formation and global evolution is thereby controlled by
advection of angular momentum from large scales, the efficiency of magnetic
braking and the resistivity of the medium, and the internal thermal and
magnetic pressures of the disk. We perform a series of 30 simulations of a
massive star forming from the gravitational collapse of a molecular cloud
threaded by an initially-uniform magnetic field, starting from different values
for the mass of the cloud, its initial density and rotation profiles, its
rotational energy content, the magnetic field strength, and the resistivity of
the material. The gas and dust is modeled with the methods of resistive
magnetohydrodynamics, also considering radiation transport of thermal emission
and self-gravity. After the initial infall phase dominated by the gravitational
collapse, an accretion disk is formed, shortly followed by the launching of
magnetically-driven outflows. Two layers can be distinguished in the accretion
disk: a thin layer, vertically supported by thermal pressure, and a thick
layer, vertically supported by magnetic pressure. We observe the effects of
magnetic braking in the inner ~50 au of the disk at late times in our fiducial
case. The parameter study reveals that the size of the disk is mostly
determined by the density and rotation profiles of the initial mass reservoir
and not by the magnetic field strength. Magnetic pressure can slightly increase
the size of the accretion disk, while magnetic braking is more relevant in the
innermost parts of the disk as opposed to the outer disk. From the parameter
study, we infer that multiple initial conditions for the onset of gravitational
collapse are able to produce a given disk size and protostellar mass.
