Interstellar CH absorption in the diffuse interstellar medium along the sight-lines to G10.6-0.4 (W31C), W49N, and W51
Journal article, 2010
We report the detection of the ground state N, J = 1, 3/2 -> 1, 1/2 doublet of the methylidyne radical CH at similar to 532 GHz and similar to 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]/[H2] similar to 3.2 +/- 1.1 x 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 nH = n(H) + 2n(H2) ranging between 100 and 1000 cm-3).
objects: W51
ISM: clouds
clouds
submillimeter: ISM
molecular absorption
ISM: molecules
ISM: individual
star-forming regions
ISM: individual objects: W49N
cn
objects: G10.6-0.4
comparative chemistry
h-2
ISM: individual
Author
M. Gerin
Ecole Normale Superieure (ENS)
M. de Luca
Ecole Normale Superieure (ENS)
J. R. Goicoechea
Centro de Astrobiologia (CAB)
E. Herbst
Ohio State University
E. Falgarone
Ecole Normale Superieure (ENS)
B. Godard
Institut d'Astrophysique Spatiale
Ecole Normale Superieure (ENS)
T. A. Bell
California Institute of Technology (Caltech)
A. Coutens
University of Toulouse
Centre national de la recherche scientifique (CNRS)
M. Kazmierczak
Nicolaus Copernicus University
P. Sonnentrucker
Johns Hopkins University
John H Black
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
D. A. Neufeld
Johns Hopkins University
T. G. Phillips
California Institute of Technology (Caltech)
J. C. Pearson
California Institute of Technology (Caltech)
P. B. Rimmer
Ohio State University
G.E. Hassel
Ohio State University
D. C. Lis
California Institute of Technology (Caltech)
C. Vastel
University of Toulouse
Centre national de la recherche scientifique (CNRS)
F. Boulanger
Institut d'Astrophysique Spatiale
J. Cernicharo
Centro de Astrobiologia (CAB)
E. Dartois
Institut d'Astrophysique Spatiale
P. Encrenaz
Ecole Normale Superieure (ENS)
T. Giesen
University of Cologne
P. F. Goldsmith
California Institute of Technology (Caltech)
H. Gupta
California Institute of Technology (Caltech)
C. Gry
Laboratoire d'Astrophysique de Marseille
P. Hennebelle
Ecole Normale Superieure (ENS)
P. Hily-Blant
Laboratoire d'Astrophysique de Grenoble
C. Joblin
Centre national de la recherche scientifique (CNRS)
University of Toulouse
R. Kolos
Polish Academy of Sciences
J. Krelowski
Nicolaus Copernicus University
J. Martin-Pintado
Centro de Astrobiologia (CAB)
Raquel Monje
California Institute of Technology (Caltech)
B. Mookerjea
Tata Institute of Fundamental Research
M. Perault
Ecole Normale Superieure (ENS)
Carina Persson
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
R. Plume
University of Calgary
M. Salez
Ecole Normale Superieure (ENS)
M. Schmidt
Polish Academy of Sciences
J. Stutzki
University of Cologne
D. Teyssier
European Space Astronomy Centre (ESAC)
S. Yu
California Institute of Technology (Caltech)
A. Contursi
MPI fur Extraterrestrische Physik
K. Menten
Max Planck Society
T. R. Geballe
Gemini Observatory North
S. Schlemmer
University of Cologne
P. Morris
California Institute of Technology (Caltech)
W. A. Hatch
California Institute of Technology (Caltech)
M. Imram
California Institute of Technology (Caltech)
J. S. Ward
California Institute of Technology (Caltech)
E. Caux
Centre national de la recherche scientifique (CNRS)
University of Toulouse
R. Güsten
Max Planck Society
T. Klein
Max Planck Society
P. Roelfsema
Netherlands Institute for Space Research (SRON)
P. Dieleman
Netherlands Institute for Space Research (SRON)
R. Schieder
University of Cologne
N. Honingh
University of Cologne
J. Zmuidzinas
California Institute of Technology (Caltech)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 521 1 Article Number: L16- L16Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/201015115