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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 ; D.C. Lis ; M. de Luca ; J. Goicoechea ; John H. Black (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; M. Gerin ; T. Bell ; F. Boulanger ; J. Cernicharo ; A. Coutens ; E. Dartois ; M. Kazmierczak ; P. Encrenaz ; Edith Falgarone ; Thomas Geballe ; T. Giesen ; B. Godard ; P.F. Goldsmith ; C. Gry ; H. Gupta ; P. Hennebelle ; E. Herbst ; P. Hily-Blant ; C. Joblin ; R. Kołos ; J. Krełowski ; J. Martín-Pintado ; K.M. Menten ; Raquel Monje ; B. Mookerjea ; T. J. Pearson ; M. Perault ; Carina M. Persson (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; R. Plume ; M. Salez ; S. Schlemmer ; M. Schmidt ; J. Stutzki ; D. Teyssier ; C. Vastel ; S. Yu ; P. Cais ; E. Caux ; René Liseau (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; P. Morris ; P. Planesas
Astronomy & Astrophysics (0004-6361). Vol. 518 (2010), p. 108.
[Artikel, refereegranskad vetenskaplig]

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.

Denna post skapades 2010-09-17. Senast ändrad 2014-09-02.
CPL Pubid: 126554


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