A Search For Dense Gas in Quiescent Bok Globules

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Session 30 -- Star Formation, Molecular Clouds and HII Regions
Display presentation, Tuesday, 31, 1994, 9:20-6:30

[30.03] A Search For Dense Gas in Quiescent Bok Globules

B. D. Kane, D. P. Clemens (Boston University), P. C. Myers (CfA)

This study demonstrates a crucial difference between quiescent Bok globules and dark cloud cores. Seventeen small, quiescent Bok globules were probed for the molecular lines of NH$_3$ (J,K=1,1) and HC$_3$N (J$=4\rightarrow3$) using the Haystack telescope. The sources have 3$\sigma$ integrated line intensity upper limits generally less than 0.1 K-km s$^{-1}$. In terms of the reference source, TMC-2, this is less than about 10\% of the brightness of the NH$_3$ (1,1) line, and less than about 30\% of brightness of the HC$_3$N ($4\rightarrow3$) line. A simple statistical equilibrium analysis indicates that chemical abundances of NH$_3$ and HC$_3$N in these globules are diminished by factors of 10 and 6, respectively, relative to dark cloud cores. Second, for plausible globule core sizes, densities are about 6 times smaller compared to those of dark cloud cores.

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