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Interstellar OH+, H2O+ and H3O+ along the sight-line to G10.6-0.4

M. Gerin ; M. de Luca ; John H. Black (Institutionen för radio- och rymdvetenskap, Radioastronomi och astrofysik) ; J.R. Goicoechea ; E. Herbst ; D.A. Neufeld ; Edith Falgarone ; B. Godard ; T. C. Pearson ; D.C. Lis ; T.G. Phillips ; T. Bell ; P. Sonnentrucker ; F. Boulanger ; J. Cernicharo ; A. Coutens ; E. Dartois ; P. Encrenaz ; T. Giesen ; P.F. Goldsmith ; H. Gupta ; C. Gry ; P. Hennebelle ; P. Hily-Blant ; C. Joblin ; M. Kazmierczak ; R. Kolos ; J. Krelowski ; J. Martin-Pintado ; Raquel Monje (Institutionen för radio- och rymdvetenskap, Avancerad mottagarutveckling) ; B. Mookerjea ; M. Perault ; Carina M. Persson (Institutionen för radio- och rymdvetenskap, Radioastronomi och astrofysik) ; R. Plume ; P.B. Rimmer ; M Salez ; M. Schmidt ; J. Stutzki ; D. Teyssier ; C. Vastel ; S. Yu ; A. Contursi ; K. Menten ; Thomas Geballe ; S. Schlemmer ; R. Shipman ; A.G.G.M. Tielens ; S. Philipp-May ; A Cros ; J. Zmuidzinas ; L.A. Samoska ; K. Klein ; A. Lorenzani
Astronomy & Astrophysics (0004-6361). Vol. 518 (2010), p. 110.
[Artikel, refereegranskad vetenskaplig]

We report the detection of absorption lines by the reactive ions OH+, H2O+ and H3O+ along the line of sight to the submillimeter continuum source G10.6$-$0.4 (W31C). We used the Herschel HIFI instrument in dual beam switch mode to observe the ground state rotational transitions of OH+ at 971 GHz, H2O+ at 1115 and 607 GHz, and H3O+ at 984 GHz. The resultant spectra show deep absorption over a broad velocity range that originates in the interstellar matter along the line of sight to G10.6$-$0.4 as well as in the molecular gas directly associated with that source. The OH+ spectrum reaches saturation over most velocities corresponding to the foreground gas, while the opacity of the H2O+ lines remains lower than 1 in the same velocity range, and the H3O+ line shows only weak absorption. For LSR velocities between 7 and 50 kms$^{-1}$ we estimate total column densities of $N$(OH+) $> 2.5 \times 10^{14}$ cm$^{-2}$, $N$(H2O+) $\sim 6 \times 10^{13}$ cm$^{-2}$ and $N$(H3O+) $\sim 4.0 \times 10^{13}$ cm$^{-2}$. These detections confirm the role of O$^+$ and OH$^+$ in initiating the oxygen chemistry in diffuse molecular gas and strengthen our understanding of the gas phase production of water. The high ratio of the OH+ by the H2O+ column density implies that these species predominantly trace low-density gas with a small fraction of hydrogen in molecular form.

Nyckelord: ISM: general; ISM: molecules; ISM: clouds

Published in Astronomy & Astrophysics special issue:
Herschel: the first science highlights


Denna post skapades 2010-09-17. Senast ändrad 2015-07-02.
CPL Pubid: 126555


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Institutioner (Chalmers)

Institutionen för radio- och rymdvetenskap, Radioastronomi och astrofysik (2005-2010)
Institutionen för radio- och rymdvetenskap, Avancerad mottagarutveckling (2005-2010)



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