The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars V. A Characterization of Protostellar Multiplicity

Abstract

We characterize protostellar multiplicity in the Orion molecular clouds using ALMA 0.87 mm and VLA 9 mm continuum surveys toward 328 protostars. These observations are sensitive to projected spatial separations as small as ∼20 au, and we consider source separations up to 10 4 au 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 10 4 au. 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

A 16 au Binary in the Class 0 Protostar L1157 MMS

“…This is one of the closest Class 0 proto-binary systems known. Its angular and physical separation is smaller than the most compact multiple systems observed by Tobin et al (2016Tobin et al ( , 2021 in the VLA and ALMA Nascent Disk and Multiplicity (VANDAM) Surveys. We examined the data in several ways to ensure the robustness of our detection detection of two sources within L1157 MMS, and we outline the additional analysis in the Appendix.…”

“…L1157 MMS is one of the most compact Class 0 multiple systems. Its separation of ∼16 au is more compact than the detections found in large surveys for protostellar multiplicity (Tobin et al 2016(Tobin et al , 2021. The wealth of complementary data on this system also enables us to put this detection in the context of the known envelope properties (Looney et al 2007;Chiang et al 2012;Maury et al 2019), envelope rotation at small and larger scales (Tobin et al 2011;Gaudel et al 2020), the outflow (Bachiller et al 2001;Kwon et al 2015;Podio et al 2016), and magnetic fields (Stephens et al 2013).…”