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

TY - JOUR

T1 - Water deuterium fractionation in the high-mass star-forming region G34.26+0.15 based on Herschel/HIFI data

AU - Coutens, Audrey

AU - Vastel, C.

AU - Hincelin, U.

AU - Herbst, E.

AU - Lis, D. C.

AU - Chavarría, L.

AU - Gérin, M.

AU - van der Tak, F. F. S.

AU - Persson, C. M.

AU - Goldsmith, P. F.

AU - Caux, E.

PY - 2014/12/1

Y1 - 2014/12/1

N2 - Understanding water deuterium fractionation is important for constraining the mechanisms of water formation in interstellar clouds. Observations of HDO and H18 2 O 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 H18 2 O 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.

AB - Understanding water deuterium fractionation is important for constraining the mechanisms of water formation in interstellar clouds. Observations of HDO and H18 2 O 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 H18 2 O 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.

KW - astrochemistry/ ISM: abundances/ ISM: individual objects: G34.26+0.15/ ISM: molecules

U2 - 10.1093/mnras/stu1816

DO - 10.1093/mnras/stu1816

M3 - Journal article

SN - 0035-8711

VL - 445

SP - 1299

EP - 1313

JO - Royal Astronomical Society. Monthly Notices

JF - Royal Astronomical Society. Monthly Notices

IS - 2

ER -