Falgarone, E. and Phillips, T. G. and Lis, D. C. and Bell, T. A. and Monje, R. and Zmuidzinas, J. (2010) CH^+(1–0) and ^(13)CH^+(1–0) absorption lines in the direction of massive star-forming regions. Astronomy and Astrophysics, 521 . Art. No. L15. ISSN 0004-6361 http://resolver.caltech.edu/CaltechAUTHORS:20110111-093157375
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We report the detection of the ground-state rotational transition of the methylidyne cation CH^+ and its isotopologue ^(13)CH^+ toward the remote massive star-forming regions W33A, W49N, and W51 with the HIFI instrument onboard the Herschel satellite. Both lines are seen only in absorption against the dust continuum emission of the star-forming regions. The CH^+ absorption is saturated over almost the entire velocity ranges sampled by the lines-of-sight that include gas associated with the star-forming regions (SFR) and Galactic foreground material. The CH^+ column densities are inferred from the optically thin components. A lower limit of the isotopic ratio [^(12)CH^+]/[^(13)CH^+] > 35.5 is derived from the absorptions of foreground material toward W49N. The column density ratio, N(CH^+)/N(HCO^+), is found to vary by at least a factor 10, between 4 and >40, in the Galactic foreground material. Line-of-sight ^(12)CH^+ average abundances relative to total hydrogen are estimated. Their average value, N(CH^+)/N_H > 2.6 × 10^(−8), is higher than that observed in the solar neighborhood and confirms the high abundances of CH^+ in the Galactic interstellar medium. We compare this result to the predictions of turbulent dissipation regions (TDR) models and find that these high abundances can be reproduced for the inner Galaxy conditions. It is remarkable that the range of predicted N(CH^+)/N(HCO^+) ratios, from 1 to ~50, is comparable to that observed.
|Additional Information:||© 2010 ESO. Received 31 May 2010, Accepted 19 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. Appendix (page 6) is only available in electronic form at http://www.aanda.org. HIFI has been designed and built by a consortium of institutes and university departments from across Europe, Canada and the United States (NASA) under the leadership of SRON, 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. MG and EF acknowledge the support from the Centre National de Recherche Spatiale (CNES). DCL is supported by the NSF, award AST-0540882 to the CSO. M.S. is supported from grant N20339334 from Polish MNiSW.|
|Subject Keywords:||astrochemistry – ISM: molecules – ISM: kinematics and dynamics – turbulence|
|Official Citation:||CH+(1–0) and 13CH+(1–0) absorption lines in the direction of massive star-forming regions E. Falgarone, B. Godard, J. Cernicharo, M. De Luca, M. Gerin, T. G. Phillips, J. H. Black, D. C. Lis, T. A. Bell, F. Boulanger, A. Coutens, E. Dartois, P. Encrenaz, T. Giesen, J. R. Goicoechea, P. F. Goldsmith, H. Gupta, C. Gry, P. Hennebelle, E. Herbst, P. Hily-Blant, C. Joblin, M. Kaźmierczak, R. Kołos, J. Krełowski, J. Martin-Pintado, R. Monje, B. Mookerjea, D. A. Neufeld, M. Perault, J. C. Pearson, C. Persson, R. Plume, M. Salez, M. Schmidt, P. Sonnentrucker, J. Stutzki, D. Teyssier, C. Vastel, S. Yu, K. Menten, T. R. Geballe, S. Schlemmer, R. Shipman, A. G. G. M. Tielens, S. Philipp, A. Cros, J. Zmuidzinas, L. A. Samoska, K. Klein, A. Lorenzani, R. Szczerba, I. Péron, P. Cais, P. Gaufre, A. Cros, L. Ravera, P. Morris, S. Lord and P. Planesas A&A 521 L15 (2010) DOI: 10.1051/0004-6361/201015109|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Benjamin Perez|
|Deposited On:||11 Jan 2011 18:05|
|Last Modified:||26 Dec 2012 12:50|
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