Cyanide and isocyanide abundances in the cold, dark cloud TMC-1 |
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Authors: | Irvine W M Schloerb F P |
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Institution: | Department of Physics and Astronomy, University of Massachusetts, USA. |
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Abstract: | We have observed emission from HCN, H13CN, HC15N, HN13C, H15NC, HC3N, CH3CN, and possibly CH3NC, and determined an upper limit for NH2CN, toward the cold, dark cloud TMC-1. The abundance ratio HNC]/HCN] = 1.55 +/- 0.16 is at least a factor approximately 4 and approximately 100 greater than that observed toward the giant molecular clouds DR 21(OH) and Orion KL, respectively. In contrast, for the corresponding methylated isomers we obtain CH3NC]/CH3CN] < or approximately 0.1. We also find NH2CN]/CH3CN] < or approximately 0.1 and HC3N]/CH3CN] = 30 +/- 10. We find no evidence for anomalous hyperfine ratios for H13CN, indicating that the ratios for HCN (cf. recent work of Walmsley et al.) are the result of self-absorption by cold foreground gas. |
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