Water in the envelopes and disks around young high-mass stars

Single-dish spectra and interferometric maps of (sub-)millimeter lines of (H2O)-O-18 and HDO are used to study the chemistry of water in eight regions of high-mass star formation. The spectra indicate HDO excitation temperatures of similar to 110 K and column densities in an 11 '' beam of similar to 2x10(14) cm(-2) for HDO and similar to 2x10(17) cm(-2) for H2O, with the N(HDO)/N(H2O) ratio increasing with decreasing temperature. Simultaneous observations of CH3OH and SO2 indicate that 20-50% of the single-dish line flux arises in the molecular outflows of these objects. The outflow contribution to the (H2O)-O-18 and HDO emission is estimated to be 10-20%. Radiative transfer models indicate that the water abundance is low (similar to 10(-6)) outside a critical radius corresponding to a temperature in the protostellar envelope of approximate to 100 K, and jumps to H2O/H-2 similar to 10(-4) inside this radius. This value corresponds to the observed abundance of solid water and together with the derived HDO/H2O abundance ratios of similar to 10(-3) suggests that the origin of the observed water is evaporation of grain mantles. This idea is confirmed in the case of AFGL 2591 by interferometer observations of the HDO 1(10)-1(11), (H2O)-O-18 3(13)-2(20) and SO2 12(0.12)-1(11.11) lines, which reveal compact (empty set similar to 800 AU) emission with a systematic velocity gradient. This size is similar to that of the 1.3 mm continuum towards AFGL 2591, from which we estimate a mass of approximate to 0.8 M-circle dot, or similar to 5% of the mass of the central star. We speculate that we may be observing a circumstellar disk in an almost face-on orientation.