Odin observations of H2O in the Galactic Centre

The Odin satellite has been used to detect emission and absorption in the 557-GHz H 216O line in the Galactic Centre towards the SgrA* Circumnuclear Disk (CND), and the SgrA +20 km s -1 and +50 km s -1 molecular clouds. Strong broad H 2O emission lines have been detected in all three objects. Narrow H 2O absorption lines are present at all three positions and originate along the lines of sight in the 3-kpc Spiral Arm, the -30 km s -1 Spiral Arm and the Local Sgr Spiral Arm. Broad H 2O absorption lines near -130 km s -1 are also observed, originating in the Expanding Molecular Ring. A new molecular feature (the "High Positive Velocity Gas" - HPVG) has been identified in the positive velocity range of $\approx$+120 to +220 km s -1, seen definitely in absorption against the stronger dust continuum emission from the +20 km s -1 and +50 km s -1 clouds and possibly in emission towards the position of SgrA* CND. The 548-GHz H 218O isotope line towards the CND is not detected at the 0.02 K (rms) level. (Note: Some of the scientific symbols can not be represented correctly in the abstract. Please read with caution and refer to the original publication.