First Detection in Space of the High-energy Isomer of Cyanomethanimine: H2CNCN
Abstract
We report the first detection in the interstellar medium of N-cyanomethanimine (H2CNCN), 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 ≤ J up ≤ 11 and K a ≤ 2 that belong to this species toward 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 H2CNCN of (2.9 ± 0.1) × 1012 cm‑2, which translates into a total molecular abundance with respect to H2 of (2.1 ± 0.3) × 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 ± 1.8 and a Z/E-HNCHCN ratio of 4.5 ± 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 (CH2NH) and the cyanogen radical (CN) arises as the primary formation route.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 2024
- DOI:
- 10.3847/1538-4357/ad3af3
- arXiv:
- arXiv:2404.03334
- Bibcode:
- 2024ApJ...967...39S
- Keywords:
-
- Astrochemistry;
- Galactic center;
- Interstellar molecules;
- Interstellar clouds;
- Spectral line identification;
- Pre-biotic astrochemistry;
- 75;
- 565;
- 849;
- 834;
- 2073;
- 2079;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 22 pages, 8 figures, 3 tables, 2 appendix - Accepted for publication in The Astrophysical Journal