First detection in space of the high-energy isomer of cyanomethanimine: H2CNCN
| Autor: | Andrés, David San, Rivilla, Víctor M., Colzi, Laura, Jiménez-Serra, Izaskun, Martín-Pintado, Jesús, Megías, Andrés, López-Gallifa, Álvaro, Martínez-Henares, Antonio, Massalkhi, Sarah, Zeng, Shaoshan, Sanz-Novo, Miguel, Tercero, Belén, de Vicente, Pablo, Martín, Sergio, Requena-Torres, Miguel A., Molpeceres, Germán, de la Concepción, Juan García |
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| Rok vydání: | 2024 |
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| Druh dokumentu: | Working Paper |
| DOI: | 10.3847/1538-4357/ad3af3 |
| Popis: | We report the first detection in the interstellar medium of $N$-cyanomethanimine (H$_2$CNCN), the stable dimer of HCN of highest energy, and the most complex organic molecule identified in space containing the prebiotically relevant NCN backbone. We have identified a plethora of $a$-type rotational transitions with 3 $\leq J_\text{up} \leq$ 11 and $K_\text{a} \leq$ 2 that belong to this species towards the Galactic Center G+0.693-0.027 molecular cloud, the only interstellar source showing the three cyanomethanimine isomers (including the $Z$- and $E$- isomers of $C$-cyanomethanimine, HNCHCN). We have derived a total column density for H$_2$CNCN of (2.9$\, \pm \,$0.1)$\times$10$^{12}$ cm$^{-2}$, which translates into a total molecular abundance with respect to H$_2$ of (2.1$\, \pm \,$0.3)$\times$10$^{-11}$. We have also revisited the previous detection of $E$- and $Z$-HNCHCN, and found a total $C/N$-cyanomethanimine abundance ratio of 31.8$\, \pm \,$1.8 and a $Z/E$-HNCHCN ratio of 4.5$\, \pm \,$0.2. While the latter can be explained on the basis of thermodynamic equilibrium, chemical kinetics are more likely responsible for the observed $C/N$-cyanomethanimine abundance ratio, where the gas-phase reaction between methanimine (CH$_2$NH) and the cyanogen radical (CN) arises as the primary formation route. Comment: 22 pages, 8 figures, 3 tables, 2 appendix - Accepted for publication in The Astrophysical Journal |
| Databáze: | arXiv |
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