Detection of OH+ and H2O+ towards Orion KL
Gupta, H. and Rimmer, P. and Pearson, J.C. and Yu, S. and Herbst, E. and Harada, N. and Bergin, E.A. and Neufeld, D.A. and Melnick, G.J. and Bachiller, R. and Bells, T.A. and Blake, G.A. and Caux, E. and Ceccarelli, C. and Cernicharo, J. and Chattopadhyay, G. and Comito, C. and Cabrit, S. and Crockett, N.R. and Daniel, F. and Falgarone, E. and Diez-Gonzalez, M.C. and Dubernet, M.-L. and Erickson, N. and Emprechtinger, M. and Encrenaz, P. and Gerin, M. and Gill, J.J. and Giesen, T.F. and Goicoechea, J.R. and Goldsmith, P.F. and Joblin, C. and Johnstone, D. and Langer, W.D. and Larsson, B. and Latter, W.B. and Lin, R.J. and Lis, D.C. and Liseau, R. and Lord, S.D. and Maiwald, F.W. and Maret, S. and Martin, P.G. and Martin-Pintado, J. and Menten, K.M. and Morris, P. and Muller, H.S.P. and Murphy, J.A. and Nordh, L.H. and Olberg, M. and Ossenkopf, V. and Pagani, L. and Perault, M. and Phillips , T.G. and Plume, R. and Qin, S.-L. and Salez, M. and Samoska, L.A. and Schilke, P. and Schlecht, E. and Schlemmer, S. and Szczerba, R. and Stutzki, J. and Trappe, N. and van der Tak, F.F.S. and Vastel, C. and Wang, S. and Yorke, H.W. and Zmuidzinas, J. and Boogert, A. and Gusten, R. and Hartogh, P. and Honigh, N. and Karpov, A. and Kooi, J. and Krieg, J.-M. and Schieder, R. and Zaal, P. (2010) Detection of OH+ and H2O+ towards Orion KL. Astronomy & Astrophysics, 521 (L47). pp. 1-5. ISSN 0004-6361
We report observations of the reactive molecular ions OH+, H2O+, and H3O+ towards Orion KL with Herschel/HIFI. All three N = 1−0 finestructure transitions of OH+ at 909, 971, and 1033 GHz and both fine-structure components of the doublet ortho-H2O+ 111−000 transition at 1115 and 1139 GHz were detected; an upper limit was obtained for H3O+. OH+ and H2O+ are observed purely in absorption, showing a narrow component at the source velocity of 9 km s−1, and a broad blueshifted absorption similar to that reported recently for HF and para-H18 2 O, and attributed to the low velocity outflow of Orion KL.We estimate column densities of OH+ and H2O+ for the 9 kms−1 component of 9±3×1012 cm−2 and 7±2×1012 cm−2, and those in the outflow of 1.9±0.7×1013 cm−2 and 1.0±0.3×1013 cm−2. Upper limits of 2.4×1012 cm−2 and 8.7×1012 cm−2 were derived for the column densities of ortho and para-H3O+ from transitions near 985 and 1657 GHz. The column densities of the three ions are up to an order of magnitude lower than those obtained from recent observations ofW31C and W49N. The comparatively low column densities may be explained by a higher gas density despite the assumption of a very high ionization rate.
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