Abstract
Context. Ketene was detected in the interstellar medium (ISM) in 1977. Until now, only one derivative, the ketenyl radical, has been observed in this medium. Due to its large dipole moment value, cynaoketene is one of the best candidates for possible ketene derivative detection. Aims. To date, the measurements of the rotational spectra have been limited to 60 GHz. The extrapolation of the prediction in the millimeter wave domain is inaccurate and does not permit an unambiguous detection. Methods. The rotational spectra were re-investigated up to 330 GHz. Using the new prediction cyanoketene was sought after in a variety of astronomical sources: NGS 63341, SgrB2(N), and ASAI sources. Results. A total of 1594 transitions were newly assigned and fitted together with those from previous studies, reaching quantum numbers up to J = 82 and Ka = 24. Watson’s asymmetric top Hamiltonian in the Ir representation was used for the analysis; both reductions A and S were tested. Logically, the S reduction gave the best results confirming that the molecule is very close to the prolate limit. Cynaoketene was not found in ISM; upper limits to the column density were derived in each source.
Highlights
Ketene was detected in the interstellar medium (ISM) more than 43 years ago (Turner 1977), and the only derivative, the ketenyl radical (HC=C=O), was observed 38 years later (Agúndez et al 2015)
Cyanides represent a ubiquitous group of large astronomical molecules in the ISM, and are some of the most abundant and detectable in a wide range of environments
Using lab conditions to reproduce the chemistry on the interstellar grains, cyanoketene was found in the photolysis of cyanoacetylene with an oxygen atom generated from ozone, the photolysis of water with cyanoacetylene (Guennoun et al 2005) or dicyanoacetylene (Guennoun et al 2004)
Summary
Ketene (ethenone, H2C=C=O) was detected in the interstellar medium (ISM) more than 43 years ago (Turner 1977), and the only derivative, the ketenyl radical (HC=C=O), was observed 38 years later (Agúndez et al 2015). Cyanides represent a ubiquitous group of large astronomical molecules in the ISM, and are some of the most abundant and detectable in a wide range of environments. Simple cyanides, such as HCN, are found in most astronomical environments ranging from comets to external galaxies. Combined with its physical properties and the presence of potential precursors in the ISM push us to record and analyze its millimetric spectrum Using these species as both physical and chemical diagnostics can provide a better understanding and calibration of the physical environments where these species are found and of the formation of large astronomical molecules in general
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