Herschel/HIFI measurements of the ortho/para ratio in water towards Sagittarius B2(M) and W31C

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Lis, D.C., Phillips, T.G., Goldsmith, P.F., Neufeld, D.A., Herbst, E., Comito, C., Schilke, P., Muller, H.S.P., Bergin, E.A., Gerin, M., Bell, T.A., Emprechtinger, M., Black, J., Blake, G.A., Boulanger, F., Caux, E., Ceccarelli, C., Cernicharo, J., Coutens, A., Crockett, N.R., Daniel, F., Dartois, E., De Luca, M., Dubernet, M.-L., Encrenaz, P., Falgarone, E., Geballe, T.R., Godard, B., Giesen, T.F., Goicoechea, J.R., Gry, C., Gupta, H., Hennebelle, P., Hily-Blant, P., Kolos, R., Krelowski, J., Joblin, C., Johnstone, D., Kazmierczak, M., Lord, S.D., Maret, S., Martin, P.G., Martin-Pintado, J., Melnick, G.J., Menten, K.M., Monjel, R., Mookerjea, B., Morris, P., Murphy, J.Anthony, Ossenkopf, V., Pearson, J.C., Perault, M., Persson, C., Plume, R., Qin, S.-L., Salez, M., Schlemmer, S., Schmidt, M., Sonnentrucker, P., Stutzki, J., Teyssier, D., Trappe, Neil, van der Tak, F.F.S., Vastel, C., Wang, S., Yorke, H.W., Yu, S., Zmuidzinas, J., Boogert, A., Erickson, N., Karpov, A., Kooi, J., Maiwald, F.W., Schieder, R. and Zaal, P. (2010) Herschel/HIFI measurements of the ortho/para ratio in water towards Sagittarius B2(M) and W31C. Astronomy & Astrophysics, 521 (L26). pp. 1-5. ISSN 0004-6361

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Abstract

We present Herschel/HIFI observations of the fundamental rotational transitions of ortho- and para-H16 2 O and H18 2 O in absorption towards Sagittarius B2(M) and W31C. The ortho/para ratio in water in the foreground clouds on the line of sight towards these bright continuum sources is generally consistent with the statistical high-temperature ratio of 3, within the observational uncertainties. However, somewhat unexpectedly, we derive a low ortho/para ratio of 2.35±0.35, corresponding to a spin temperature of ∼27 K, towards Sagittarius B2(M) at velocities of the expanding molecular ring. Water molecules in this region appear to have formed with, or relaxed to, an ortho/para ratio close to the value corresponding to the local temperature of the gas and dust.

Item Type:	Article
Additional Information:	© ESO 2010 The original publication is available at DOI: 10.1051/0004-6361/201015072
Keywords:	astrochemistry; ISM; abundances; molecules; molecular processes; submillimeter; Herschel/HIFI;
Academic Unit:	Faculty of Science and Engineering > Experimental Physics
Item ID:	4024
Depositing User:	Dr. Anthony Murphy
Date Deposited:	05 Dec 2012 16:17
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
Refereed:	Yes
Related URLs:	http://www.aanda.org/ http://publications.edpsciences.org/
URI:	https://mural.maynoothuniversity.ie/id/eprint/4024
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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Herschel/HIFI measurements of the ortho/para ratio in water towards Sagittarius B2(M) and W31C

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