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Interstellar CH absorption in the diffuse interstellar medium along the sight-lines to G10.6–0.4 (W31C), W49N, and W51

Gerin, M. and Bell, T. A. and Phillips, T. G. and Lis, D. C. and Monje, R. and Morris, P. and Zmuidzinas, J. (2010) Interstellar CH absorption in the diffuse interstellar medium along the sight-lines to G10.6–0.4 (W31C), W49N, and W51. Astronomy and Astrophysics, 521 . Art. No. L16. ISSN 0004-6361.

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We report the detection of the ground state N, J = 1, 3/2 → 1, 1/2 doublet of the methylidyne radical CH at ~532 GHz and ~536 GHz with the Herschel/HIFI instrument along the sight-line to the massive star-forming regions G10.6–0.4 (W31C), W49N, and W51. While the molecular cores associated with these massive star-forming regions show emission lines, clouds in the diffuse interstellar medium are detected in absorption against the strong submillimeter background. The combination of hyperfine structure with emission and absorption results in complex profiles, with overlap of the different hyperfine components. The opacities of most of the CH absorption features are linearly correlated with those of CCH, CN, and HCO^+ in the same velocity intervals. In specific narrow velocity intervals, the opacities of CN and HCO^+ deviate from the mean trends, giving rise to more opaque absorption features. We propose that CCH can be used as another tracer of the molecular gas in the absence of better tracers, with [CCH]/[H_2] ~3.2 ± 1.1 × 10^(−8). The observed [CN]/[CH], [CCH]/[CH] abundance ratios suggest that the bulk of the diffuse matter along the lines of sight has gas densities n_H = n(H) + 2n(H_2) ranging between 100 and 1000 cm^(−3).

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Lis, D. C.0000-0002-0500-4700
Additional Information:© 2010 ESO. Received 31 May 2010, Accepted 9 July 2010, Published online 01 October 2010. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Appendices A and B (pages 6, 7) are only available in electronic form at HIFI has been designed and built by a consortium of institutes and university departments from across Europe, Canada, and the United States under the leadership of SRON, the Netherlands Institute for Space Research, Groningen, The Netherlands, and with major contributions from Germany, France and the US. Consortium members are: Canada: CSA, U. Waterloo; France: CESR, LAB, LERMA, IRAM; Germany: KOSMA, MPIfR, MPS; Ireland: NUI Maynooth; Italy: ASI, IFSI-INAF, Osservatorio Astrofisico di Arcetri-INAF; Netherlands: SRON, TUD; Poland: CAMK, CBK; Spain Observatorio Astronòmico Nacional (IGN), Centro de Astrobiologia; Sweden: Chalmers University of Technology – MC2, RSS & GARD, Onsala Space Observatory, Swedish National Space Board, Stockholm University – Stockholm Observatory; Switzerland: ETH Zurich, FHNW; USA: CalTech, JPL, NHSC. M.G., E.F., M.D.L. acknowledge the support from the Centre National de Recherche Spatiale (CNES), and from ANR through the SCHISM project (ANR- 09-BLAN-231). JRG was supported by a Ramon y Cajal contract and by the MICINN/AYA2009-07304 and and CSD2009-00038 grants.
Funding AgencyGrant Number
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Agence Nationale pour la Recherche (ANR)ANR-09-BLAN-231
Ramón y Cajal ProgrammeUNSPECIFIED
Ministerio de Ciencia e Innovación (MCINN)AYA2009-07304
Ministerio de Ciencia e Innovación (MCINN)CSD2009-00038
Subject Keywords:ISM: clouds – ISM: molecules – submillimeter: ISM – ISM: individual objects: G10.6-0.4 – ISM: individual objects: W49N – ISM: individual objects: W51
Record Number:CaltechAUTHORS:20110111-111805895
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Official Citation:Interstellar CH absorption in the diffuse interstellar medium along the sight-lines to G10.6–0.4 (W31C), W49N, and W51 M. Gerin, M. De Luca, J. R. Goicoechea, E. Herbst, E. Falgarone, B. Godard, T. A. Bell, A. Coutens, M. Kaźmierczak, P. Sonnentrucker, J. H. Black, D. A. Neufeld, T. G. Phillips, J. Pearson, P. B. Rimmer, G. Hassel, D. C. Lis, C. Vastel, F. Boulanger, J. Cernicharo, E. Dartois, P. Encrenaz, T. Giesen, P. F. Goldsmith, H. Gupta, C. Gry, P. Hennebelle, P. Hily-Blant, C. Joblin, R. Kołos, J. Krełowski, J. Martín-Pintado, R. Monje, B. Mookerjea, M. Perault, C. Persson, R. Plume, M. Salez, M. Schmidt, J. Stutzki, D. Teyssier, S. Yu, A. Contursi, K. Menten, T. R. Geballe, S. Schlemmer, P. Morris, W. A. Hatch, M. Imram, J. S. Ward, E. Caux, R. Güsten, T. Klein, P. Roelfsema, P. Dieleman, R. Schieder, N. Honingh and J. Zmuidzinas A&A 521 L16 (2010) DOI: 10.1051/0004-6361/201015115
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21698
Deposited By: Benjamin Perez
Deposited On:11 Jan 2011 22:08
Last Modified:31 Aug 2017 03:10

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