Physical conditions in shocked regions of Orion from ground-based observations of H2O

We present observations of the 5(15)-4(22) transition of water vapor at 325.15 GHz taken with the Caltech Submillimeter Observatory telescope toward Orion IRc2. The emission is more extended than that of other molecular species such as CH3OH. However, it is much less extended than the emission of water vapor at 183.31 GHz reported in an earlier paper by Cernicharo and coworkers. A comparison of the line intensities at 325.15 and 183.31 GHz puts useful constraints on the density and temperature of the emitting regions and allows an estimate of H2O abundance, x(H2O), of similar or equal to 10(-4) in the Plateau and similar or equal to 10(-6) to 10(-5) in the Ridge.