Substructure and Fragmentation in Starless Cores

We present ALMA observations of 73 starless and protostellar cores in the Orion B North molecular cloud. In Band 3, we detect a total of 34 continuum sources, of which 4 appear to be starless. We use synthetic observations of simulations to compute the expected number of starless cores. We find at least one starless core should be detectable, consistent with our data.

We also run a virial analysis of the cores to put the Orion B North observations into context with similar previous ALMA surveys of cores in Chamaeleon and Ophiuchus and conclude that the Chamaeleon I starless core population is characteristically less bounded. These differences may explain why the Chamaeleon I cores do not follow the turbulent fragmentation model predictions, while the Ophiuchus and Orion B North cores are consistent with the model.