SMA OBSERVATIONS OF CLASS 0 PROTOSTARS: A HIGH ANGULAR RESOLUTION SURVEY OF PROTOSTELLAR BINARY SYSTEMS
- Purple Mountain Observatory, Chinese Academy of Sciences, 2 West Beijing Road, Nanjing 210008 (China)
- Department of Astronomy, Yale University, Box 208101, New Haven, CT 06520-8101 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany)
- Niels Bohr Institute and Centre for Star and Planet Formation, Copenhagen University, Juliane Maries Vej 30, DK-2100 Copenhagen O (Denmark)
- Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan (China)
- Institute for Astrophysical Research, Boston University, Boston, MA 02215 (United States)
We present high angular resolution 1.3 mm and 850 {mu}m dust continuum data obtained with the Submillimeter Array toward 33 Class 0 protostars in nearby clouds (distance < 500 pc), which represents so far the largest survey toward protostellar binary/multiple systems. The median angular resolution in the survey is 2.''5, while the median linear resolution is approximately 600 AU. Compact dust continuum emission is observed from all sources in the sample. Twenty-one sources in the sample show signatures of binarity/multiplicity, with separations ranging from 50 AU to 5000 AU. The numbers of singles, binaries, triples, and quadruples in the sample are 12, 14, 5, and 2, respectively. The derived multiplicity frequency (MF) and companion star fraction (CSF) for Class 0 protostars are 0.64 {+-} 0.08 and 0.91 {+-} 0.05, respectively, with no correction for completeness. The derived MF and CSF in this survey are approximately two times higher than the values found in the binary surveys toward Class I young stellar objects, and approximately three (for MF) and four (for CSF) times larger than the values found among main-sequence stars, with a similar range of separations. Furthermore, the observed fraction of high-order multiple systems to binary systems in Class 0 protostars (0.50 {+-} 0.09) is also larger than the fractions found in Class I young stellar objects (0.31 {+-} 0.07) and main-sequence stars ({<=}0.2). These results suggest that binary properties evolve as protostars evolve, as predicted by numerical simulations. The distribution of separations for Class 0 protostellar binary/multiple systems shows a general trend in which CSF increases with decreasing companion separation. We find that 67% {+-} 8% of the protobinary systems have circumstellar mass ratios below 0.5, implying that unequal-mass systems are preferred in the process of binary star formation. We suggest an empirical sequential fragmentation picture for binary star formation, based on this work and existing lower resolution single-dish observations.
- OSTI ID:
- 22126765
- Journal Information:
- Astrophysical Journal, Vol. 768, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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