Issue |
A&A
Volume 693, January 2025
|
|
---|---|---|
Article Number | L20 | |
Number of page(s) | 7 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202453459 | |
Published online | 28 January 2025 |
Letter to the Editor
Detection of thioacetaldehyde (CH3CHS) in TMC-1: Sulfur-oxygen differentiation along the hydrogenation sequence⋆
1
Instituto de Física Fundamental, CSIC, Calle Serrano 123, E-28006 Madrid, Spain
2
Observatorio Astronómico Nacional, IGN, Calle Alfonso XII 3, E-28014 Madrid, Spain
3
Observatorio de Yebes, IGN, Cerro de la Palera s/n, E-19141 Yebes, Guadalajara, Spain
⋆⋆ Corresponding authors; marcelino.agundez@csic.es; jose.cernicharo@csic.es
Received:
16
December
2024
Accepted:
7
January
2025
In recent years, the chemistry of sulfur in the interstellar medium has experienced renewed interest due to the detection of a large variety of molecules containing sulfur. We report the first identification in space of a new S-bearing molecule, thioacetaldehyde (CH3CHS), which is the sulfur counterpart of acetaldehyde (CH3CHO). The astronomical observations are part of QUIJOTE, a Yebes 40 m Q-band line survey of the cold dense cloud TMC-1. We detected seven individual lines corresponding to A and E components of the four most favorable rotational transitions of CH3CHS covered in the Q band (31.0–50.3 GHz). Assuming a rotational temperature of 9 K, we derive a column density of 9.8 × 1010 cm−2 for CH3CHS, which implies that it is 36 times less abundant than its oxygen counterpart CH3CHO. By comparing the column densities of the O- and S-bearing molecules detected in TMC-1, we find that as molecules increase their degree of hydrogenation, sulfur-bearing molecules become less abundant than their oxygen analog. That is, hydrogenation seems to be less favored for S-bearing molecules than for O-bearing ones in cold sources such as TMC-1. We explored potential formation pathways to CH3CHS and implemented them into a chemical model, which underestimates the observed abundance of thioacetaldehyde by several orders of magnitude, however. Quantum chemical calculations carried out for one of the potential formation pathways, the S + C2H5 reaction, indicate that formation of CH3CHS is only a minor channel in this reaction.
Key words: astrochemistry / line: identification / ISM: molecules / radio lines: ISM / ISM: individual objects: TMC-1
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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