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We present Atacama Large Millimeter/submillimeter Array (ALMA) observationsof multiple protostar systems in the Perseus molecular cloud previouslydetected by the Karl G. Jansky Very Large Array (VLA). We observed 17 close($<$600~AU separation) multiple systems at 1.3~mm in continuum and fivemolecular lines (i.e., \twco, \cateo, \thco, H$_2$CO, SO) to characterize thecircum-multiple environments in which these systems are forming. We detect atleast one component in the continuum for the 17 multiple systems. In threesystems, one companion is not detected, and for two systems the companions areunresolved at our observed resolution. We also detect circum-multiple dustemission toward 8 out of 9 Class 0 multiples. Circum-multiple dust emission isnot detected toward any of the 8 Class I multiples. Twelve systems are detectedin the dense gas tracers toward their disks/inner envelopes. For these 12systems, we use the dense gas observations to characterize their formationmechanism. The velocity gradients in the circum-multiple gas are clearlyorthogonal to the outflow directions in 8 out of the 12 systems, consistentwith disk fragmentation. Moreover, only two systems with separations $<$200~AUare \textit{inconsistent} with disk fragmentation, in addition to the twowidest systems ($>$500~AU). Our results suggest that disk fragmentation viagravitational instability is an important formation mechanism for closemultiple systems, but further statistics are needed to better determine therelative fraction formed via this method.

astrophysical journal/the astrophysical journal

The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Perseus  Protostars. VI. Characterizing the Formation Mechanism for Close Multiple  Systems