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

Abstract

ABSTRACT 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 (8 mm and 1 cm) and C-band (4 and 6.6 cm). The observed sample has a bolometric luminosity range between 0.1 L ⊙ and ∼33 L ⊙, with a median of 0.7 L ⊙. This multiplicity study is based on the Ka-band data, having a best resolution of ∼0.″065 (15 au) and separations out 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 ∼75 au and another peak at ∼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.