CS Emission from Bok Globules: Survey Results

Abstract

We present the results of a survey for CS emission toward a sample of 47 Bok globules selected from the catalog of Clemens & Barvainis. The globules were observed at the FCRAO 14 m, the SEST 15 m, and the IRAM 30 m telescopes in the CS J = 2 → 1 transition. Additionally, higher spatial resolution (11''-30'') observations in the CS J = 3 → 2 and 5 → 4 lines, as well as the C34S J = 2 → 1 and 3 → 2 lines, were carried out toward a subsample of 20 globules using the IRAM 30 m and the CSO 10 m telescopes. Two-thirds of the globules were detected in the CS J = 2 → 1 line. The detection rate was higher in globules with IRAS sources (72%) than in globules without IRAS sources (44%). The detection rate was 100% for globules with embedded Class 0 and Class I infrared sources, dropping to 60% for Class II-D sources and to 40% for Class II sources. These results support the association of dense cores with IRAS point sources in Bok globules and indicate that the dense gas is most apparent in the early stages. We present CS maps of 12 globule cores and derive sizes for nine CS cores. The results of the CS survey are compared with the results of surveys of other lines and of dust continuum emission. The integrated intensities of the CS lines correlate with those of C18O J = 2 → 1, but the line widths and FWHM sizes tend to be somewhat larger than those of C18O. The mean FWHM size of those sources with reasonable distance estimates is 0.41 ± 0.18 pc, and the mean virial mass is 60 ± 52 M☉. The mean size places them intermediate between cores in Taurus and cores associated with water masers and massive star formation.