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 O rion IRc2. The emission is more extended than that of other molecular speci es such as CH3OH. However, it is much less extended than the emission of wa ter vapor at 183.31 GHz reported in an earlier paper by Cernicharo and cowo rkers. A comparison of the line intensities at 325.15 and 183.31 GHz puts u seful constraints on the density and temperature of the emitting regions an d 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.