Formation of multiple protostellar systems.

Fluid-dynamic calculations of the isothermal collapse of a rotating protostellar core are presented which predict the formation of multiple fragments. The initial model is assumed to have a moderate central condensation with a small amplitude, m = 2 perturbation. Initial fragmentation into a low-mode configuration results as a consequence of the gravitational growth of non-axisymmetric instabilities. Rotation-driven fragmentation, later in the evolution, involves a time-sequential formation of new condensations from other dense regions of the collapsing core. The deforming effects of rotation could be a leading mechanism for determining the irregular geometry of the resulting systems as observed in nature.