Herschel observations of deuterated water towards Sgr B2(M)
Comito, C. and Schilke, P. and Rolffs, R. and Lis, D.C. and Belloche, A. and Bergin, E.A. and Phillips , T.G. and Bell, T.A. and Crockett, N.R. and Wang, S. and Blake, G.A. and Caux, E. and Ceccarelli, C. and Cernicharo, J. and Daniel, F. and Dubernet, M.-L. and Emprechtinger, M. and Encrenaz, P. and Gerin, M. and Giesen, T.F. and Goicoechea, J.R. and Goldsmith, P.F. and Gupta, H. and Herbst, E. and Joblin, C. and Johnstone, D. and Langer, W.D. and Latter, W.D. and Lord, S.D. and Maret, S. and Martin, P.G. and Melnick, G.J. and Menten, K.M. and Morris, P. and Muller, H.S.P. and Murphy, J.A. and Neufeld, D.A. and Ossenkopf, V. and Pearson, J.C. and Perault, M. and Plume, R. and Qin, S.-L. 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 Olberg, M. and Szczerba, R. and Larsson, B. and Liseau, R. and Lin, R.H. and Samoska, L.A. and Schlecht, E. (2010) Herschel observations of deuterated water towards Sgr B2(M). Astronomy & Astrophysics, 521 (L38). pp. 1-5. ISSN 0004-6361
Observations of HDO are an important complement for studies of water, because they give strong constraints on the formation processes – grain surfaces versus energetic process in the gas phase, e.g. in shocks. The HIFI observations of multiple transitions of HDO in Sgr B2(M) presented here allow the determination of the HDO abundance throughout the envelope, which has not been possible before with ground-based observations only. The abundance structure has been modeled with the spherical Monte Carlo radiative transfer code RATRAN, which also takes radiative pumping by continuum emission from dust into account. The modeling reveals that the abundance of HDO rises steeply with temperature from a low abundance (2.5 × 10−11) in the outer envelope at temperatures below 100 K through a medium abundance (1.5 × 10−9) in the inner envelope/outer core at temperatures between 100 and 200 K, and finally a high abundance ( 3.5 × 10−9) at temperatures above 200 K in the hot core.
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