Strong absorption by interstellar hydrogen fluoride: Herschel/HIFI observations of the sight-line to G10.6-0.4 (W31C)

D. A. Neufeld P. Sonnentrucker T. G. Phillips 1 D. C. Lis 1 M. De Luca 2 J. R. Goicoechea 2 J. H. Black M. Gerin 2, 3 T. Bell 4 F. Boulanger 5 J. Cernicharo 6 A. Coutens 4 E. Dartois 5 M. Kazmierczak P. Encrenaz 2 E. Falgarone 3 T. R. Geballe T. Giesen B. Godard P. F. Goldsmith C. Gry 7 H. Gupta 8 P. Hennebelle 4 E. Herbst 9 P. Hily-Blant 4 C. Joblin 10 R. Kolos J. Krelowski J. Martin-Pintado 4 K. M. Menten 11 R. Monje B. Mookerjea 12 Justin Pearson 4 M. Perault 3 C. Persson 13 R. Plume M. Salez 4 S. Schlemmer M. Schmidt 14 J. Stutzki 4 D. Teyssier 15 C. Vastel 10 S. Yu Ph. Cais 16, 17, 18, 19 E. Caux 10 R. Liseau P. Morris P. Planesas
Abstract : We report the detection of strong absorption by interstellar hydrogen fluoride along the sight-line to the submillimeter continuum source G10.6-0.4 (W31C). We have used Herschel's HIFI instrument, in dual beam switch mode, to observe the 1232.4763 GHz J=1-0 HF transition in the upper sideband of the Band 5a receiver. The resultant spectrum shows weak HF emission from G10.6-0.4 at LSR velocities in the range -10 to -3 km/s, accompanied by strong absorption by foreground material at LSR velocities in the range 15 to 50 km/s. The spectrum is similar to that of the 1113.3430 GHz 1(11)-0(00) transition of para-water, although at some frequencies the HF (hydrogen fluoride) optical depth clearly exceeds that of para-H2O. The optically-thick HF absorption that we have observed places a conservative lower limit of 1.6E+14 cm-2 on the HF column density along the sight-line to G10.6-0.4. Our lower limit on the HF abundance, 6E-9 relative to hydrogen nuclei, implies that hydrogen fluoride accounts for between ~ 30 and 100% of the fluorine nuclei in the gas phase along this sight-line. This observation corroborates theoretical predictions that - because the unique thermochemistry of fluorine permits the exothermic reaction of F atoms with molecular hydrogen - HF will be the dominant reservoir of interstellar fluorine under a wide range of conditions.
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Contributeur : Marie-Paule Pomies <>
Soumis le : mardi 28 septembre 2010 - 11:41:09
Dernière modification le : vendredi 22 mars 2019 - 01:41:25

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D. A. Neufeld, P. Sonnentrucker, T. G. Phillips, D. C. Lis, M. De Luca, et al.. Strong absorption by interstellar hydrogen fluoride: Herschel/HIFI observations of the sight-line to G10.6-0.4 (W31C). Astronomy and Astrophysics - A&A, EDP Sciences, 2010, 518, pp.108. 〈10.1051/0004-6361/201014523〉. 〈hal-00521637〉



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