Issue |
A&A
Volume 677, September 2023
|
|
---|---|---|
Article Number | L13 | |
Number of page(s) | 6 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202347524 | |
Published online | 13 September 2023 |
Letter to the Editor
Aromatic cycles are widespread in cold clouds⋆
1
Instituto de Física Fundamental, CSIC, Calle Serrano 123, 28006 Madrid, Spain
e-mail: marcelino.agundez@csic.es
2
Observatorio Astronómico Nacional, IGN, Calle Alfonso XII 3, 28014 Madrid, Spain
3
Observatorio de Yebes, IGN, Cerro de la Palera s/n, 19141 Yebes, Guadalajara, Spain
Received:
21
July
2023
Accepted:
29
August
2023
We report the detection of large hydrocarbon cycles toward several cold dense clouds. We observed four sources (L1495B, Lupus-1A, L483, and L1527) in the Q band (31−50 GHz) using the Yebes 40 m radiotelescope. Using the line stack technique, we find statistically significant evidence of benzonitrile (C6H5CN) in L1495B, Lupus-1A, and L483 at levels of 31.8σ, 15.0σ, and 17.2σ, respectively, while there is no hint of C6H5CN in the fourth source, L1527. The column densities derived are in the range (1.7−3.8) × 1011 cm−2, which is somewhat below the value derived toward the cold dense cloud TMC-1. When we simultaneously analyze all the benzonitrile abundances derived toward cold clouds in this study and in the literature, a clear trend emerges in that the higher the abundance of HC7N, the more abundant C6H5CN is. This indicates that aromatic cycles are especially favored in those interstellar clouds where long carbon chains are abundant, which suggests that the chemical processes that are responsible for the formation of linear carbon chains are also behind the synthesis of aromatic rings. We also searched for cycles other than benzonitrile, and found evidence of indene (C9H8), cyclopentadiene (C5H6), and 1-cyano cyclopentadiene (1-C5H5CN) at levels of 9.3σ, 7.5σ, and 8.4σ, respectively, toward L1495B, which shows the strongest signal from C6H5CN. The relative abundances between the various cycles detected in L1495B are consistent – within a factor of three – with those previously found in TMC-1. It is therefore likely that not only C6H5CN but also other large aromatic cycles are abundant in clouds rich in carbon chains.
Key words: astrochemistry / line: identification / ISM: molecules / radio lines: ISM
© 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.
This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication.
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.