TMC-1, the starless core sulfur factory: Discovery of NCS, HCCS, HCCS, HCCCS, and CS and detection of CS

Abstract

We report the detection of the sulfur-bearing species NCS, HCCS, HCCS, HCCCS, and CS 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 CS 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 cm, N(HCCS) = (6.8 ± 0.6) × 10 cm, N(HCCS) = (7.8 ± 0.8) × 10 cm, N(HCCCS) = (3.7 ± 0.4) × 10 cm, N(CS) = (3.8 ± 0.4) × 10 cm, and N(CS) = (5.0 ± 1.0) × 10 cm. The observed abundance ratio between CS and CS is 340, that is to say a factor of approximately one hundred larger than the corresponding value for CCS and CS. 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.