Discovery of Interstellar trans -cyanovinylacetylene (HC ≡ CCH = CHC ≡ N) and vinylcyanoacetylene (H 2 C = CHC 3 N) in GOTHAM Observations of TMC-1
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Kelvin_Lee_2021_ApJL_908_L11.pdf
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Author(s)
Kelvin Lee, Kin Long
Loomis, Ryan A
Burkhardt, Andrew M
Cooke, Ilsa R
Xue, Ci
Siebert, Mark A
Shingledecker, Christopher N
Remijan, Anthony
Charnley, Steven B
McCarthy, Michael C
Date Issued
2021
Journal
Astrophysical Journal Letters
Publisher
American Astronomical Society
Citation
Kelvin Lee, Kin Long, Loomis, Ryan A, Burkhardt, Andrew M, Cooke, Ilsa R, Xue, Ci et al. 2021. "Discovery of Interstellar trans -cyanovinylacetylene (HC ≡ CCH = CHC ≡ N) and vinylcyanoacetylene (H 2 C = CHC 3 N) in GOTHAM Observations of TMC-1." Astrophysical Journal Letters, 908 (1).
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Author's final manuscript
Abstract
We report the discovery of two unsaturated organic species, trans-(E)-cyanovinylacetylene and vinylcyanoacetylene, using the second data release of the GOTHAM deep survey toward TMC-1 with the 100m Green Bank Telescope. For both detections, we performed velocity stacking and matched filter analyses using Markov Chain Monte Carlo simulations, and for trans-(E)-cyanovinylacetylene, three rotational lines were observed at low signal-to-noise (∼3σ). From this analysis, we derive column densities of 2 × 1011 and 3 × 1011 cm-2 for vinylcyanoacetylene and trans-(E)-cyanovinylacetylene, respectively, and an upper limit of <2 × 1011 cm-2 for trans-(Z)- cyanovinylacetylene. Comparisons with G3//B3LYP semiempirical thermochemical calculations indicate abundances of the [H3C5N] isomers are not consistent with their thermodynamic stability, and instead their abundances are mainly driven by dynamics. We provide a discussion on how these species may be formed in TMC-1, with reference to related molecules like vinyl cyanide (CH2 = CHC ≡ N). As part of this discussion, we performed the same analysis for ethyl cyanide (CH3CH2C≡N), the hydrogenation product of CH2=CHC≡N. This analysis provides evidence-at 4.2σ significance-of an upper limit to the column density of <4×1011 cm-2; an order of magnitude lower than previous upper limits toward this source.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.3847/2041-8213/ABDBB9
