Discovery of Interstellar trans-cyanovinylacetylene (HCCCH=CCHCN) and vinylcyanoacetylene (H$_2$C=CHC$_3$N) in GOTHAM Observations of TMC-1. (arXiv:2101.05858v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Lee_K/0/1/0/all/0/1">Kin Long Kelvin Lee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Loomis_R/0/1/0/all/0/1">Ryan A. Loomis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Burkhardt_A/0/1/0/all/0/1">Andrew M. Burkhardt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cooke_I/0/1/0/all/0/1">Ilsa R. Cooke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Xue_C/0/1/0/all/0/1">Ci Xue</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Siebert_M/0/1/0/all/0/1">Mark A. Siebert</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shingledecker_C/0/1/0/all/0/1">Christopher N. Shingledecker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Remijan_A/0/1/0/all/0/1">Anthony Remijan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Charnley_S/0/1/0/all/0/1">Steven B. Charnley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McCarthy_M/0/1/0/all/0/1">Michael C. McCarthy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McGuire_B/0/1/0/all/0/1">Brett A. McGuire</a>
We report the discovery of two unsaturated organic species,
trans-(E)-cyanovinylacetylene and vinylcyanoacetylene, using the second data
release of the GOTHAM deep survey towards TMC-1 with the 100 m 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 (${sim}$3$sigma$). From this analysis, we derive column
densities of $2times10^{11}$ and $3times10^{11}$ cm$^{-2}$ for
vinylcyanoacetylene and trans-(E)-cyanovinylacetylene, respectively, and an
upper limit of $<2times10^{11}$ cm$^{-2}$ for trans-(Z)-cyanovinylacetylene.
Comparisons with G3//B3LYP semi-empirical thermochemical calculations indicate
abundances of the [H$_3$C$_5$N}] isomers are not consistent with their
thermodynamic stability, and instead their abundances are mainly driven by
dynamics. We provide discussion into how these species may be formed in TMC-1,
with reference to related species like vinyl cyanide (CH$_2$=CHCN). As part of
this discussion, we performed the same analysis for ethyl cyanide
(CH$_3$CH$_2$CN), the hydrogenation product of CH$_2$=CHCN. This analysis
provides evidence — at 4.17$sigma$ significance — an upper limit to the
column density of $<4times10^{11}$ cm$^{-2}$; an order of magnitude lower than
previous upper limits towards this source.
We report the discovery of two unsaturated organic species,
trans-(E)-cyanovinylacetylene and vinylcyanoacetylene, using the second data
release of the GOTHAM deep survey towards TMC-1 with the 100 m 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 (${sim}$3$sigma$). From this analysis, we derive column
densities of $2times10^{11}$ and $3times10^{11}$ cm$^{-2}$ for
vinylcyanoacetylene and trans-(E)-cyanovinylacetylene, respectively, and an
upper limit of $<2times10^{11}$ cm$^{-2}$ for trans-(Z)-cyanovinylacetylene.
Comparisons with G3//B3LYP semi-empirical thermochemical calculations indicate
abundances of the [H$_3$C$_5$N}] isomers are not consistent with their
thermodynamic stability, and instead their abundances are mainly driven by
dynamics. We provide discussion into how these species may be formed in TMC-1,
with reference to related species like vinyl cyanide (CH$_2$=CHCN). As part of
this discussion, we performed the same analysis for ethyl cyanide
(CH$_3$CH$_2$CN), the hydrogenation product of CH$_2$=CHCN. This analysis
provides evidence — at 4.17$sigma$ significance — an upper limit to the
column density of $<4times10^{11}$ cm$^{-2}$; an order of magnitude lower than
previous upper limits towards this source.
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