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Published March 1994 | Published
Journal Article Open

Structure and chemistry in the northwestern condensation of the Serpens molecular cloud core


We present single-dish and interferometric observations of gas and dust in the core of the Serpens molecular cloud, focusing on the northwestern condensation. Single-dish molecular line observations are used to probe the structure and chemistry of the condensation while high-resolution images of CS and CH_(3)0H are combined with continuum observations from λ = 1.3 mm to λ = 3.5 cm to study the subcondensations and overall distribution of dust. For the northwestern condensation, we derive a characteristic density of 3 x 10^5 cm^(-3) and an estimated total mass of approximately 70 M_⊙. We find compact molecular emission associated with the far-infrared source S68 FIRS 1, and with a newly detected subcondensation named S68 N. Comparison of the large-and small-scale emission reveals that most of the material in the northwest condensation is not directly associated with these compact sources, suggesting a youthful age for this region. CO J = 1 approaches 0 observations indicate widespread outflow activity. However, no unique association of embedded objects with outflows is possible with our observations. The SiO emission is found to be extended with the overall emission centered about S68 FIRS 1; the offset of the peak emission from all of the known continuum sources and the coincidence between the blueshifted SiO emission and blueshifted high-velocity gas traced by CO and CS is consistent with formation of SiO in shocks. Derived abundances of CO and HCO^(+) are consistent with quiescent and other star-forming regions while CS, HCN, and H2CO abundances indicate mild depletions within the condensation. Spectral energy distribution fits to S68 FIRS 1 indicate a modest luminosity (50-60 L_⊙), implying that it is a low-mass (0.5-3 M_⊙) young stellar object. Radio continuum observations of the triple source toward S68 FIRS 1 indicate that the lobe emission is varying on timescales ≤ 1 yr while the central component is relatively constant over ~14 yr. The nature of a newly detected compact emission region, S68 N, is less certain due to the absence of firm continuum detections; based on its low luminosity (<5 L_⊙) and strong molecular emission, S68 N may be prestellar subcondensation of gas and dust.

Additional Information

© 1994 American Astronomical Society. Received 1993 May 28; accepted 1993 September 23. We would like to thank the following individuals whose help was important in obtaining the large amount of observations necessary for this project: Phil Jewell and the telescope operators of the NRAO 12m; Tom Phillips, Jocelyn Keene, and Antony Schinkel (CSO); Rick Forster, Marc Warnock, and Al Masters (BIMA); Barry Clark (VLA). Special thanks to T. Groesbeck, J. Howe, and T. Helfer for help with observations. This work was sponsored by National Science Foundation grant AST 91-00306 and by NASA grant 01526111. G. A. Blake acknowledges support from the David & Lucille Packard and Alfred P. Sloan Foundations, and NASA grant NAGW-2297.

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August 22, 2023
August 22, 2023