THE VLA NASCENT DISK AND MULTIPLICITY SURVEY OF PERSEUS PROTOSTARS (VANDAM). II. MULTIPLICITY OF PROTOSTARS IN THE PERSEUS MOLECULAR CLOUD

We present a multiplicity study of all known protostars (94) in the Perseus molecular cloud from a Karl G. Jansky Very Large Array survey at Ka-band (8mm and 1 cm) and C-band (4 and 6.6 cm). The observed sample has a bolometric luminosity range between 0.1 L-circle dot and similar to 33 L-circle dot, with a median of 0.7 L-circle dot. This multiplicity study is based on the Ka-band data, having a best resolution of similar to 0.'' 065 (15 au) and separations out to similar to 43 '' (10,000 au) can be probed. The overall multiplicity fraction (MF) is found to be 0.40 +/- 0.06 and the companion star fraction (CSF) is 0.71 +/- 0.06. The MF and CSF of the Class 0 protostars are 0.57 +/- 0.09 and 1.2 +/- 0.2, and the MF and CSF of Class I protostars are both 0.23 +/- 0.08. The distribution of companion separations appears bi-modal, with a peak at similar to 75 au and another peak at similar to 3000 au. Turbulent fragmentation is likely the dominant mechanism on >1000 au scales and disk fragmentation is likely to be the dominant mechanism on <200 au scales. Toward three Class 0 sources we find companions separated by <30 au. These systems have the smallest separations of currently known Class 0 protostellar binary systems. Moreover, these close systems are embedded within larger (50-400 au) structures and may be candidates for ongoing disk fragmentation.