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Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2010

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

Emmanuel Dartois

Résumé

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 km s-1 we estimate total column densities of N(OH+) >= 2.5 × 1014 cm-2, N(H2O+) ~6 × 1013 cm-2 and N(H3O+) ~4.0 × 1013 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.

Dates et versions

hal-03742424 , version 1 (02-08-2022)

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Maryvonne Gerin, Massimo de Luca, John H. Black, Javier R. Goicoechea, Eric Herbst, et al.. Interstellar OH+, H2O+ and H3O+ along the sight-line to G10.6-0.4. Astronomy and Astrophysics - A&A, 2010, 518, pp.L110. ⟨10.1051/0004-6361/201014576⟩. ⟨hal-03742424⟩
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