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Detection of interstellar HCS and its metastable isomer HSC: New pieces in the puzzle of sulfur chemistry

AuthorsAgúndez, Marcelino ; Marcelino, Nuria ; Cernicharo, José ; Tafalla, M.
KeywordsLine: identification
Radio lines: ISM
ISM: molecules
ISM: clouds
Issue Date14-Mar-2018
CitationAstronomy and Astrophysics 611: L1 (2018)
AbstractWe present the first identification in interstellar space of the thioformyl radical (HCS) and its metastable isomer HSC. These species were detected toward the molecular cloud L483 through observations carried out with the IRAM 30 m telescope in the λ3 mm band. We derive beam-averaged column densities of 7 × 10 cm for HCS and 1.8 × 10 cm for HSC, which translate into fractional abundances relative to H of 2 × 10 and 6 × 10, respectively. Although the amount of sulfur locked by these radicals is low, their detection allows placing interesting constraints on the chemistry of sulfur in dark clouds. Interestingly, the HCS/HCS abundance ratio is found to be quite low, ~1, in contrast with the oxygen analog case, in which the HCO/HCO abundance ratio is around 10 in dark clouds. Moreover, the radical HCS is found to be more abundant than its oxygen analog, HCO. The metastable species HOC, the oxygen analog of HSC, has not yet been observed in space. These observational constraints are compared with the outcome of a recent model of the chemistry of sulfur in dark clouds. The model underestimates the fractional abundance of HCS by at least one order of magnitude, overestimates the HCS/HCS abundance ratio, and does not provide an abundance prediction for the metastable isomer HSC. These observations should prompt a revision of the chemistry of sulfur in interstellar clouds.
Description4 pags., 2 figs., 1 tab.
Publisher version (URL)https://doi.org/10.1051/0004-6361/201832743
Identifiersdoi: 10.1051/0004-6361/201832743
issn: 1432-0746
Appears in Collections:(CFMAC-IFF) Artículos
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