GRAVITATIONAL COLLAPSE AND FRAGMENTATION OF CENTRALLY CONDENSED PROTOSTELLAR CORES

The protostellar collapse of mildly centrally condensed, rotating cores is investigated for initial configurations with varying thermal energy (alpha) and degree of central condensation (eta). An m = 4 density variation, which resulted in quadruple protostellar formation for initially uniform-density clouds with low and intermediate a (less than or similar 0.25), is used to perturb the centrally condensed cores. Thus the models may better represent oblate rather than prolate cores. Independently of the initial conditions, all centrally condensed models evolved through similar intermediate forms, producing a final near-equilibrium, off-axis fragment. The size (D(f)), mass (M(f)) and specific angular momentum (J(f)/M(f)) of the forming fragments decrease with decreasing alpha and increasing eta. In all cases, fragmentation does not result in an efficient mechanism to induce a net loss of the a/m (is-proportional-to J(f)/M(f)2) ratio as expected from stellar observations. The absence of high-order fragmentation in the present models, even for initially low alpha (= 0.05), implies that centrally condensed oblate cores may be less likely to evolve into multiple protostellar systems during the first dynamical collapse than are centrally condensed prolate-like clumps, as shown by recent calculations.