A PRODUCTION MECHANISM FOR CLUSTERS OF DENSE CORES

Collapse and fragmentation processes within filamentary interstellar m olecular clouds are investigated in detail. A quasi-equilibrium filame nt fragments into dense cores separated by about 4 times the filament diameter. Nonlinear calculations reveal that the central region of eac h core tends toward spherical collapse and further hierarchical fragme ntation is not expected. However, merging and clustering of cores tend to occur soon after the fragmentation. When the line mass of an isoth ermal filament exceeds the critical value for equilibrium by a small a mount, perturbations do not grow much, and the entire filament collaps es toward the axis without fragmenting. In this case no characteristic scale for fragmentation appears during the isothermal collapse phase. Subsequent evolution is also investigated. A change of the equation o f state yields a characteristic density, separation length, and mass f or fragmentation. These values correspond to 5 x 10(-15) g cm(-3), 2 x 10(-3) pc, and 4 x 10(-2) M., if the cloud temperature is 10 K. These results are consistent with recent high-resolution radio observations of dense cores in Taurus dark cloud.