We characterize protostellar multiplicity in the Orion molecular clouds using Atacama Large Millimeter/submillimeter Array 0.87mm and Very Large Array 9mm continuum surveys toward 328 protostars. These observations are sensitive to projected spatial separations as small as ~20au, and we consider source separations up to 104au as potential companions. The overall multiplicity fraction (MF) and companion fraction (CF) for the Orion protostars are 0.30+/-0.03 and 0.44+/-0.03, respectively, considering separations from 20 to 104au. The MFs and CFs are corrected for potential contamination by unassociated young stars using a probabilistic scheme based on the surface density of young stars around each protostar. The companion separation distribution as a whole is double peaked and inconsistent with the separation distribution of solar-type field stars, while the separation distribution of Flat Spectrum protostars is consistent solar-type field stars. The multiplicity statistics and companion separation distributions of the Perseus star-forming region are consistent with those of Orion. Based on the observed peaks in the Class 0 separations at ~100au and ~103au, we argue that multiples with separations =103au result primarily from turbulent fragmentation. We also find that MFs/CFs may rise from Class 0 to Flat Spectrum protostars between 100 and 103au in regions of high young stellar object density. This finding may be evidence for the migration of companions from >103au to <103au, and that some companions between 103 and 104au must be (or become) unbound.

Cone search capability for table J/ApJ/925/39/table1 (Orion catalog)

Cone search capability for table J/ApJ/925/39/table2 (Perseus catalog)