Volume 518, July-August 2010
Herschel: the first science highlights
|Number of page(s)||5|
|Published online||16 July 2010|
Letter to the Editor
First detection of the methylidyne cation (CH+) fundamental rotational line with the Herschel/SPIRE FTS*
Institute for Space Imaging Science, University of Lethbridge, Alberta, Canada e-mail: firstname.lastname@example.org
2 Institut d'Astrophysique Spatiale, CNRS/Université Paris-Sud 11, 91405 Orsay, France
3 Laboratoire d'Astrophysique de Marseille, UMR6110 CNRS, 38 rue F. Joliot-Curie, 13388 Marseille, France
4 Space Science Department, Rutherford Appleton Laboratory, Chilton, UK
5 Department of Physics and Astronomy, Cardiff University, Cardiff, UK
6 CEA, Laboratoire AIM, Irfu/SAp, Orme des Merisiers, 91191 Gif-sur-Yvette, France
7 Centre d'Étude Spatiale des Rayonnements, CNRS/Université de Toulouse, 9 Avenue du colonel Roche, BP 44346, 31028 Toulouse Cedex 04, France
8 Canadian Institute for Theoretical Astrophysics, Toronto, Ontario, M5S 3H8, Canada
9 CNRS/INSU, Laboratoire d'Astrophysique de Bordeaux, UMR 5804, BP 89, 33271 Floirac Cedex, France
10 University of California, Radio Astronomy Laboratory, Berkeley, 601 Campbell Hall, US Berkeley CA 94720-3411, USA
11 Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, 38406 Saint-Martin-d'Hères, France
12 Joint Astronomy Centre, University Park, Hilo, USA
13 Blue Sky Spectroscopy Inc, Lethbridge, Canada
14 National Astronomical Observatories, PR China
15 CNRS, UMR5187, 31028 Toulouse, France
16 Istituto di Fisica dello Spazio Interplanetario, INAF, via del Fosso del Cavaliere 100, 00133 Roma, Italy
17 NASA – Goddard SFC, USA
18 Department of Physics and Astronomy, The Open University, Milton Keynes MK7 6AA, UK
Accepted: 4 May 2010
Aims. To follow the species chemistry arising in diverse sources of the Galaxy with Herschel.
Methods. SPIRE FTS sparse sampled maps of the Orion bar & compact HII regions G29.96-0.02 and G32.80+0.19 have been analyzed.
Results. Beyond the wealth of atomic and molecular lines detected in the high-resolution spectra obtained with the FTS of SPIRE in the Orion Bar, one emission line is found to lie at the position of the fundamental rotational transition of CH+ as measured precisely in the laboratory by Pearson and Drouion. This coincidence suggests that it is the first detection of the fundamental rotational transition of CH+. This claim is strengthened by the observation of the lambda doublet transitions arising from its relative, CH, which are also observed in the same spectrum. The broad spectral coverage of the SPIRE FTS allows for the simultaneous measurement of these closely related chemically species, under the same observing conditions. The importance of these lines are discussed and a comparison with results obtained from models of the photon dominated region (PDR) of Orion are presented. The CH+ line also appears in absorption in the spectra of the two galactic compact HII regions G29.96-0.02 and G32.80+0.19, which is likely due to the presence of CH+ in the the cold neutral medium of the galactic plane. These detections will shed light on the formation processes and on the existence of CH+, which are still outstanding questions in astrophysics.
Key words: ISM: molecules / evolution / ISM: general / space vehicles: instruments / techniques: spectroscopic
© ESO, 2010
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