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Discovery of far-infrared pure rotational transitions of CH+ in NGC 7027

Cernicharo, J; Liu, XW; GonzalezAlfonso, E; Cox, P; Barlow, MJ; Lim, T; Swinyard, BM; (1997) Discovery of far-infrared pure rotational transitions of CH+ in NGC 7027. Astrophysical Journal , 483 (1) L65-L68. 10.1086/310729. Green open access

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Abstract

We report the discovery of the rotational spectrum of CH+ in the Infrared Space Observatory Long Wavelength Spectrometer (LWS) spectrum of the planetary nebula NGC 7027. The identification relies on a 1996 reanalysis of the LWS spectrum by Liu et al. and on new LWS data. The strong line at 179.62 μm (coinciding with the 212-101 transition of water vapor) and the lines at 119.90 and 90.03 μm (reported as unidentified by Liu et al.), whose frequencies are in the harmonic relation 2 : 3:4, are shown to arise from the J = 2-1, 3-2, and 4-3 rotational transitions of CH+. This identification is strengthened by the new LWS spectra of NGC 7027, which clearly show the next two rotational lines of CH+ at 72.140 and 60.247 μm. This is the first time that the pure rotational spectrum of CH+ has been observed. This discovery opens the possibility of probing the densest and warmest zones of photodissociation regions. We derive a rotational temperature for the CH+ lines of 150 ± 20 K and a CH+/CO abundance ratio of 2-6 × 10-4.

Type: Article
Title: Discovery of far-infrared pure rotational transitions of CH+ in NGC 7027
Open access status: An open access version is available from UCL Discovery
DOI: 10.1086/310729
Publisher version: https://doi.org/10.1086/310729
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/10095240
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