Issue |
A&A
Volume 672, April 2023
|
|
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Article Number | L13 | |
Number of page(s) | 13 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202346467 | |
Published online | 21 April 2023 |
Letter to the Editor
The magnesium paradigm in IRC +10216: Discovery of MgC4H+, MgC3N+, MgC6H+, and MgC5N+⋆
1
Grupo de Astrofísica Molecular, Instituto de Física Fundamental (IFF-CSIC), C/ Serrano 121, 28006 Madrid, Spain
e-mail: jose.cernicharo@csic.es, carlos.cabezas@csic.es
2
Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
3
Observatorio Astronómico Nacional (OAN, IGN), Madrid, Spain
4
Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 Saint Martin d’Hères, France
5
Department of Applied Chemistry, Science Building II, National Yang Ming Chiao Tung University, 1001 Ta-Hsueh Rd., Hsinchu 300098, Taiwan
Received:
20
March
2023
Accepted:
5
April
2023
We found four series of harmonically related lines in IRC +10216 with the Yebes 40 m and IRAM 30 m telescopes. The first series corresponds to a molecule with a rotational constant, B, of 1448.5994±0.0013 MHz and a distortion constant, D, of 63.45±1.15 Hz and covers upper quantum numbers from Ju = 11 up to 33 (B1449). The second series is fitted with B = 1446.9380±0.0098 MHz and D = 91±23 Hz and covers upper quantum numbers from Ju = 11 up to 17 (B1447). The third series is fitted with B = 598.7495±0.0011 MHz and D = 6.13±0.43 Hz and covers quantum numbers from Ju = 26 up to 41 (B599). Finally, the frequencies of the last series of lines can be reproduced with B = 594.3176±0.0026 MHz and D = 4.92±1.16 Hz (B594). The large values of D point toward four metal-bearing carriers. After exploring all plausible candidates containing Na, Al, Mg, and other metals, our ab initio calculations indicate that the cations MgC4H+, MgC3N+, MgC6H+, and MgC5N+ must be the carriers of B1449, B1447, B599, and B594, respectively. These cations could be formed by the radiative association of Mg+ with C4H, C3N, C6H, and C5N, respectively. We calculated the radiative association rate coefficient of Mg+ with C4H, C3N, C6H, and C5N and incorporated them in our chemical model. The results confirm that the Mg-bearing cations can be formed through these radiative association reactions in the outer layers of IRC +10216. This is the first time that cationic metal-bearing species have been found in space. These results provide a new paradigm on the reactivity of ionized metals with abundant radicals and open the door for further characterization of similar species in metal-rich astrophysical environments.
Key words: molecular data / line: identification / ISM: molecules / ISM: individual objects: IRC + 10216 / ISM: individual objects: TMC-1 / astrochemistry
Based on observations carried out with the Yebes 40 m telescope (projects 19A010, 20A017, 20B014, 21A019) and IRAM 30 m telescope. The 40 m radio telescope at Yebes Observatory is operated by the Spanish Geographic Institute (IGN, Ministerio de Fomento). IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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