Title: The dependence of protostar formation on the geometry and strength of the initial magnetic field,
Abstract: We report results from twelve simulations of the collapse of a molecular
cloud core to form one or more protostars, comprising three field strengths
(mass-to-flux ratios, {\mu}, of 5, 10, and 20) and four field geometries (with
values of the angle between the field and rotation axes, {\theta}, of 0°,
20°, 45°, and 90°), using a smoothed particle
magnetohydrodynamics method. We find that the values of both parameters have a
strong effect on the resultant protostellar system and outflows. This ranges
from the formation of binary systems when {\mu} = 20 to strikingly differing
outflow structures for differing values of {\theta}, in particular highly
suppressed outflows when {\theta} = 90°. Misaligned magnetic fields can
also produce warped pseudo-discs where the outer regions align perpendicular to
the magnetic field but the innermost region re-orientates to be perpendicular
to the rotation axis. We follow the collapse to sizes comparable to those of
first cores and find that none of the outflow speeds exceed 8 km s$^{-1}$.
These results may place constraints on both observed protostellar outflows, and
also on which molecular cloud cores may eventually form either single stars and
binaries: a sufficiently weak magnetic field may allow for disc fragmentation,
whilst conversely the greater angular momentum transport of a strong field may
inhibit disc fragmentation.