TMC-1, the starless core sulfur factory: Discovery of NCS, HCCS, H<sub>2</sub>CCS, H<sub>2</sub>CCCS, and C<sub>4</sub>S and detection of C<sub>5</sub>S
J. Cernicharo, C. Cabezas, M. Agúndez, B. Tercero, J. R. Pardo, N. Marcelino, J. D. Gallego, F. Tercero, J. A. López-Pérez, P. de Vicente
Abstract
We report the detection of the sulfur-bearing species NCS, HCCS, H 2 CCS, H 2 CCCS, and C 4 S for the first time in space. These molecules were found towards TMC-1 through the observation of several lines for each species. We also report the detection of C 5 S for the first time in a cold cloud through the observation of five lines in the 31–50 GHz range. The derived column densities are N (NCS) = (7.8 ± 0.6) × 10 11 cm −2 , N (HCCS) = (6.8 ± 0.6) × 10 11 cm −2 , N (H 2 CCS) = (7.8 ± 0.8) × 10 11 cm −2 , N (H 2 CCCS) = (3.7 ± 0.4) × 10 11 cm −2 , N (C 4 S) = (3.8 ± 0.4) × 10 10 cm −2 , and N (C 5 S) = (5.0 ± 1.0) × 10 10 cm −2 . The observed abundance ratio between C 3 S and C 4 S is 340, that is to say a factor of approximately one hundred larger than the corresponding value for CCS and C 3 S. The observational results are compared with a state-of-the-art chemical model, which is only partially successful in reproducing the observed abundances. These detections underline the need to improve chemical networks dealing with S-bearing species.