Herschel observations of EXtra-Ordinary Sources (HEXOS): Observations of H2O and its isotopologues towards Orion KL

Melnick, G.J. and Tolls, V. and Neufeld, D.A. and Bergin, E.A. and Phillips , T.G. and Wang, S. and Crockett, N.R. and Bell, T.A. and Blake, G.A. and Cabrit, S. and Caux, E. and Ceccarelli, C. and Cernicharo, J. and Comito, C. and Daniel, F. and Dubernet, M.-L. and Emprechtinger, M. and Encrenaz, P. and Falgarone, E. and Gerin, M. and Giesen, T.F. and Goicoechea, J.R. and Goldsmith, P.F. and Herbst, E. and Joblin, C. and Johnstone, D. and Langer, W.D. and Latter, W.D. and Lis, D.C. and Lord, S.D. and Maret, S. and Martin, P.G. and Menten, K.M. and Morris, P. and Muller, H.S.P. and Murphy, J.A. and Ossenkopf, V. and Pagani, L. and Pearson, J.C. and Perault, M. and Plume, R. and Qin, S.-L. and Salez, M. and Schilke, P. and Schlemmer, S. and Stutzki, J. and Trappe, N. and van der Tak, F.F.S. and Vastel, C. and Yorke, H.W. and Yu, S. and Zmuidzinas, J. (2010) Herschel observations of EXtra-Ordinary Sources (HEXOS): Observations of H2O and its isotopologues towards Orion KL. Astronomy & Astrophysics, 521 (L27). pp. 1-5. ISSN 0004-6361

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We report the detection of more than 48 velocity-resolved ground rotational state transitions of H 16 2 O, H 18 2 O, and H 17 2 O – most for the first time – in both emission and absorption toward Orion KL using Herschel/HIFI. We show that a simple fit, constrained to match the known emission and absorption components along the line of sight, is in excellent agreement with the spectral profiles of all the water lines. Using the measured H 18 2 O line fluxes, which are less affected by line opacity than their H 16 2 O counterparts, and an escape probability method, the column densities of H 18 2 O associated with each emission component are derived. We infer total water abundances of 7.4 × 10−5, 1.0× 10−5, and 1.6 × 10−5 for the plateau, hot core, and extended warm gas, respectively. In the case of the plateau, this value is consistent with previous measures of the Orion-KL water abundance as well as those of other molecular outflows. In the case of the hot core and extended warm gas, these values are somewhat higher than water abundances derived for other quiescent clouds, suggesting that these regions are likely experiencing enhanced water-ice sublimation from (and reduced freeze-out onto) grain surfaces due to the warmer dust in these sources.

Item Type: Article
Additional Information: © ESO 2010 The original publication is available at DOI: 10.1051/0004-6361/201015085
Keywords: ISM; abundances; molecules; Herschel observations; EXtra-Ordinary Sources; HEXOS; H2O; isotopologues; Orion KL;
Academic Unit: Faculty of Science and Engineering > Experimental Physics
Item ID: 4019
Depositing User: Dr. Anthony Murphy
Date Deposited: 04 Dec 2012 16:18
Journal or Publication Title: Astronomy & Astrophysics
Publisher: EDP Sciences
Refereed: Yes

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