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Water deuterium fractionation in the high-mass star-forming region G34.26+0.15 based on Herschel/HIFI data

A. Coutens ; C. Vastel ; U Hincelin ; E. Herbst ; D.C. Lis ; L. Chavarría ; M. Gerin ; F. F. S. van der Tak ; Carina M. Persson (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; P.E. Goldsmith ; E. Caux
Monthly notices of the Royal Astronomical Society (0035-8711). Vol. 445 (2014), 2, p. 1299-1313.
[Artikel, refereegranskad vetenskaplig]

Understanding water deuterium fractionation is important for constraining the mechanisms of water formation in interstellar clouds. Observations of HDO and H182O transitions were carried out towards the high-mass star-forming region G34.26+0.15 with the Heterodyne Instrument for the Far-Infrared (HIFI) instrument onboard the Herschel Space Observatory, as well as with ground-based single-dish telescopes. 10 HDO lines and three H182O lines covering a broad range of upper energy levels (22–204 K) were detected. We used a non-local thermal equilibrium 1D analysis to determine the HDO/H2O ratio as a function of radius in the envelope. Models with different water abundance distributions were considered in order to reproduce the observed line profiles. The HDO/H2O ratio is found to be lower in the hot core (∼3.5 × 10−4–7.5 × 10−4) than in the colder envelope (∼1.0 × 10−3–2.2 × 10−3). This is the first time that a radial variation of the HDO/H2O ratio has been found to occur in a high-mass source. The chemical evolution of this source was modelled as a function of its radius and the observations are relatively well reproduced. The comparison between the chemical model and the observations leads to an age of ∼105 yr after the infrared dark cloud stage.

Nyckelord: astrochemistry ISM: abundances ISM: individual objects: G34.26+0.15 ISM: molecules



Denna post skapades 2014-12-21. Senast ändrad 2015-01-16.
CPL Pubid: 208828

 

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Institutioner (Chalmers)

Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik

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Astronomi

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Onsala rymdobservatorium