Abstract
Context. The majority of sulfur-containing molecules detected in the interstellar medium (ISM) are analogs of oxygen-containing compounds. Propynal was detected in the ISM in 1988, hence propynethial, its sulfur derivative, is a good target for an ISM search. Aims. Our aim is to measure the rotational spectrum of propynethial and use those measurements to search for this species in the ISM. To date, measurements of the rotational spectra of propynethial have been limited to a small number or transitions below 52 GHz. The extrapolation of the prediction to lines in the milimeter-wave domain is inaccurate and does not provide data to permit an unambiguous detection. Methods. The rotational spectrum was re-investigated up to 630 GHz. Using the new prediction lines of propynethial, as well as the related propynal, a variety of astronomical sources were searched, including star-forming regions and dark clouds. Conclusions. A total of 3288 transitions were newly assigned and fit together with those from previous studies, reaching quantum numbers up to J = 107 and Ka = 24. Watson’s symmetric top Hamiltonian in the Ir representation was used for the analysis, because the molecule is very close to the prolate limit. The search for propynethial resulted in a non-detection; upper limits to the column density were derived in each source.
Highlights
Some 23 sulfur-containing molecules have been discovered in the interstellar medium (ISM)1 (McGuire 2018)
Propynal is known in TMC-1, Sgr B2(N), and Barnard 1 from prior work (Irvine et al 1988; Turner 1991; Loison et al 2016), and we report a detection in L1527, which, to the best of our knowledge, has not been previously seen in these data
The non-detection of propynethial in the 11 different astronomical sources searched here adds to a growing list of sulfur analogs to known interstellar species that have not yet
Summary
Some 23 sulfur-containing molecules have been discovered in the interstellar medium (ISM) (McGuire 2018). The majority of these are analogs of oxygen-containing compounds, and can be extremely useful in exploring the chemistry of the ISM through comparison of reaction pathways and relative abundances. Sulfur-containing compounds are of interest, because significantly lower sulfur levels are found in dense regions of the ISM than in diffuse regions (Martín-Doménech et al 2016). Propynethial, the sulfur analog of propynal is a molecule of interest in exploring the chemistry of the ISM, and sulfur-bearing species in particular.
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