Protostellar masses versus ionization fraction in star-forming clouds

We study the dynamical evolution of self-gravitating magnetic cloud cores w ith an implicit MHD code for different dependencies of the ionization fract ion on density. Assuming magnetically subcritical cloud cores initially sim ilar in every respect except for the degree of ionization, we show that mod erately and highly ionized cores tend to form more massive objects than the ir weakly ionized counterparts. Including the effects of rotation and/or mo re efficient cooling enhances this difference. Whereas the collapse of a we akly ionized core occurs on the free-fall time scale and independent of the boundary conditions, the onset of collapse in moderately or highly ionized media depends strongly on the flow of material along magnetic field lines through the boundaries. We discuss the possibility that fast, large scale gravitationally induced i nflows are likely to occur along the lines of strong magnetic fields thread ing a highly ionized self-gravitating core. Based on our numerical results, we conclude that the ratio of mass to magnetic flux should be considered i n combination with ionization fraction in order to estimate the mass of the object which can be expected to result from non-isolated core collapse.