STAR-FORMING CORES EMBEDDED IN A MASSIVE COLD CLUMP: FRAGMENTATION, COLLAPSE, AND ENERGETIC OUTFLOWS

The fate of massive cold clumps, their internal structure, and collapse need to be characterized to understand the initial conditions for the formation of high-mass stars, stellar systems, and the origin of associations and clusters. We explore the onset of star formation in the 75 M SMM1 clump in the region ISOSS J18364-0221 using infrared and (sub-)millimeter observations including interferometry. This contracting clump has fragmented into two compact cores SMM1 North and South of 0.05 pc radius, having masses of 15 and 10 M , and luminosities of 20 L and 180 L . SMM1 South harbors a source traced at 24 and 70 mm, drives an energetic molecular outflow, and appears supersonically turbulent at the core center. SMM1 North has no infrared counterparts and shows lower levels of turbulence, but also drives an outflow. Both outflows appear collimated, and parsec-scale near-infrared features probably trace the outflow-powering jets. We derived mass outflow rates of at least 4 x 10-5 M yr-1 and outflow timescales of less than 104 yr. Our HCN(1-0) modeling for SMM1 South yielded an infall velocity of 0.14 km s-1 and an estimated mass infall rate of 3 x 10-5 M yr-1. Both cores may harbor seeds of intermediate- or high-mass stars. We compare the derived core properties with recent simulations of massive core collapse. They are consistent with the very early stages dominated by accretion luminosity.