Detection of Thioacetaldehyde (CH3CHS) in TMC-1: Sulfur-oxygen Differentiation Along The Hydrogenation Sequence
In recent years the chemistry of sulfur in the interstellar medium has experienced a renewed interest due to the detection of a large variety of molecules containing sulfur.
Here 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 40m 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 9.8e10 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 compared to their oxygen analog. That is, hydrogenation seems to be less favored for S-bearing molecules than for O-bearing ones in cold sources like TMC-1.
We explored potential formation pathways to CH3CHS and implemented them into a chemical model, which however underestimates by several orders of magnitude the observed abundance of thioacetaldehyde. 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.
M. Agundez, G. Molpeceres, C. Cabezas, N. Marcelino, B. Tercero, R. Fuentetaja, P. de Vicente, J. Cernicharo
Comments: Accepted for publication in A&A Letters
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2501.05125 [astro-ph.GA] (or arXiv:2501.05125v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2501.05125
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Submission history
From: Marcelino Agundez
[v1] Thu, 9 Jan 2025 10:28:35 UTC (481 KB)
https://arxiv.org/abs/2501.05125
Astrobiology, Astrochemistry,
