Odin water mapping in the Orion KL region

A. O. H. Olofsson, G. Olofsson, A. Hjalmarson, P. Bergman, J. H. Black, R. S. Booth, V. Buat, C. L. Curry, P. J. Encrenaz, E. Falgarone, P. Feldman, M. Fich, H. G. Floren, U. Frisk, M. Gerin, E. M. Gregersen, J. Harju, T. Hasegawa, L. E. B. Johansson, S. KwokN. F. Tothill

    Research output: Contribution to journalArticlepeer-review

    Abstract

    New results from water mapping observations of the Orion KL region using the submm/mm wave satellite Odin (2.1′ beam size at 557 GHz), are presented. The ortho-H2O JK(+)K(-) = l1.0 → l0.1 ground state transition was observed in a 7′ × 7′ rectangular grid with a spacing of 1′, while the same line of H2 18O was measured in two positions, Orion KL itself and 2′ south of Orion KL. In the main water species, the KL molecular outflow is largely resolved from the ambient cloud and it is found to have an extension of 60″-110″. The H2O outflow profile exhibits a rather striking absorption-like asymmetry at the line centre. Self-absorption in the near (or "blue") part of the outflow (and possibly in foreground quiescent halo gas) is tentatively suggested to play a role here. We argue that the dominant part of the KL H2 18O outflow emission emanates from the compact (size ∼15″) low-velocity flow and here estimate an H2O abundance of circa 10-5 compared to all H2 in the flow - an order of magnitude below earlier estimates of the H2O abundance in the shocked gas of the high-velocity flow. The narrow ambient cloud lines show weak velocity trends, both in the N-S and E-W directions. H2 18O is detected for the first time in the southern position at a level of ∼0.15 K and we here estimate an H2O abundance of (1-8) × 10-8. (Note: Some of the scientific symbols can not be represented correctly in the abstract. Please read with caution and refer to the original publication.)
    Original languageEnglish
    Pages (from-to)L47-L54
    Number of pages8
    JournalAstronomy and Astrophysics
    Volume402
    Issue number3
    DOIs
    Publication statusPublished - 2003

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