Issue |
A&A
Volume 656, December 2021
|
|
---|---|---|
Article Number | L21 | |
Number of page(s) | 12 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202142634 | |
Published online | 17 December 2021 |
Letter to the Editor
Discovery of HCCCO and C5O in TMC-1 with the QUIJOTE line survey⋆
1
Grupo de Astrofísica Molecular, Instituto de Física Fundamental (IFF-CSIC), C/ Serrano 121, 28006 Madrid, Spain
e-mail: jose.cernicharo@csic.es
2
Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
3
Observatorio Astronómico Nacional (OAN, IGN), Madrid, Spain
Received:
10
November
2021
Accepted:
26
November
2021
We report on the detection, for the first time in space, of the radical HCCCO and of pentacarbon monoxide, C5O. The derived column densities are (1.6 ± 0.2) × 1011 cm−2 and (1.5 ± 0.2) × 1010 cm−2, respectively. We have also analysed the data for all the molecular species of the families HCnO and CnO within our QUIJOTE’s line survey. Upper limits are obtained for HC4O, HC6O, C4O, and C6O. We report a robust detection of HC5O and HC7O based on 14 and 12 rotational lines detected with a signal-to-noise ratio ≥30 and ≥5, respectively. The derived N(HC3O)/N(HC5O) abundance ratio is 0.09 ± 0.03, while N(C3O)/N(C5O) is 80 ± 2, and N(HC5O)/N(HC7O) is 2.2 ± 0.3. As opposed to the cyanopolyyne family, HC2n + 1N, which shows a continuous decrease in the abundances with increasing n, the CnO and HCnO species show a clear abundance maximum for n = 3 and 5, respectively. They also show an odd and even abundance alternation, with odd values of n being the most abundant, which is reminiscent of the behaviour of CnH radicals, where in that case species with even values of n are more abundant. We explored the formation of these species through two mechanisms previously proposed, which are based on radiative associations between CnHm+ ions with CO and reactions of Cn̄ and CnH− anions with O atoms, and we found that several species, such as C5O, HC4O, and HC6O, are significantly overestimated. Our understanding of how these species are formed is incomplete as of yet. Other routes based on neutral-neutral reactions such as those of Cn and CnH carbon chains with O, OH, or HCO, could be behind the formation of these species.
Key words: molecular data / line: identification / ISM: molecules / ISM: individual objects: TMC-1 / astrochemistry
Based on observations carried out with the Yebes 40 m telescope (projects 19A003, 20A014, 20D023, and 21A011) and the Institut de Radioastronomie Millimétrique (IRAM) 30 m telescope. The 40 m radiotelescope at Yebes Observatory is operated by the Spanish Geographic Institute (IGN, Ministerio de Transportes, Movilidad y Agenda Urbana). IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).
© ESO 2021
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.