Satoshi Hamano
First Detection of A–X (0,0) Bands of Interstellar C2 and CN
Hamano, Satoshi; Kawakita, Hideyo; Kobayashi, Naoto; Takenaka, Keiichi; Ikeda, Yuji; Matsunaga, Noriyuki; Kondo, Sohei; Sameshima, Hiroaki; Fukue, Kei; Yasui, Chikako; Mizumoto, Misaki; Otsubo, Shogo; Watase, Ayaka; Yoshikawa, Tomohiro; Kobayashi, Hitomi
Authors
Hideyo Kawakita
Naoto Kobayashi
Keiichi Takenaka
Yuji Ikeda
Noriyuki Matsunaga
Sohei Kondo
Hiroaki Sameshima
Kei Fukue
Chikako Yasui
Dr Misaki Mizumoto misaki.mizumoto@durham.ac.uk
Sponsored Researcher Post
Shogo Otsubo
Ayaka Watase
Tomohiro Yoshikawa
Hitomi Kobayashi
Abstract
We report the first detection of C2 P - S +A Xu g 11 (0,0) and CN P - S +A Xu 22 (0,0) absorption bands in the interstellar medium. The detection was made using the near-infrared (0.91–1.35μm) high-resolution (R=20,000 and 68,000) spectra of Cygnus OB2 No. 12 collected with the WINERED spectrograph mounted on the 1.3m Araki telescope. The A–X (1,0) bands of C2 and CN were detected simultaneously. These near-infrared bands have larger oscillator strengths, compared with the A–X (2,0) bands of C2 and CN in the optical. In the spectrum of the C2 (0,0) band with R=68,000, three velocity components in the line of sight could be resolved and the lines were detected up to high rotational levels (J″∼20). By analyzing the rotational distribution of C2, we could estimate the kinetic temperature and gas density of the clouds with high accuracy. Furthermore, we marginally detected weak lines of 12C13C for the first time in the interstellar medium. Assuming that the rotational distribution and the oscillator strengths of the relevant transitions of 12C2 and 12C13C are the same, the carbon isotope ratio was estimated to be 12C/13C=50–100, which is consistent with the ratio in the local interstellar medium. We also constrained the oscillator strength ratio of the C2 (0,0) and (1,0) bands, for which there exists a discrepancy between theoretical calculations and experimental results. This unique constraint obtained from astronomical observation will contribute to improving the accuracy of the oscillator strength measurement, which will lead to further advancements of the C2 excitation model and allow the physical conditions of clouds to be derived.
Citation
Hamano, S., Kawakita, H., Kobayashi, N., Takenaka, K., Ikeda, Y., Matsunaga, N., Kondo, S., Sameshima, H., Fukue, K., Yasui, C., Mizumoto, M., Otsubo, S., Watase, A., Yoshikawa, T., & Kobayashi, H. (2019). First Detection of A–X (0,0) Bands of Interstellar C2 and CN. Astrophysical Journal, 881(2), Article 143. https://doi.org/10.3847/1538-4357/ab2e0f
Journal Article Type | Article |
---|---|
Acceptance Date | Jun 28, 2019 |
Online Publication Date | Aug 22, 2019 |
Publication Date | Aug 20, 2019 |
Deposit Date | Sep 13, 2019 |
Publicly Available Date | Sep 13, 2019 |
Journal | Astrophysical Journal |
Print ISSN | 0004-637X |
Publisher | American Astronomical Society |
Peer Reviewed | Peer Reviewed |
Volume | 881 |
Issue | 2 |
Article Number | 143 |
DOI | https://doi.org/10.3847/1538-4357/ab2e0f |
Public URL | https://durham-repository.worktribe.com/output/1292370 |
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Copyright Statement
© 2019. The American Astronomical Society. All rights reserved.
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