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Description
We present Herschel/HIFI observations of 14 water lines in a small sample of galactic massive protostellar objects: NGC6334I(N), DR21(OH), IRAS16272-4837, and IRAS05358+3543. Using water as a tracer of the structure and kinematics, we aim to individually study each of these objects, to estimate the amount of water around them, but to also shed light on the high-mass star formation process. We analyze the gas dynamics from the line profiles using Herschel-HIFI observations acquired as part of the WISH key-project of 14 far-IR water lines (water, H_2_^17^O, H_2_^18^O), and several other species. Then through modeling of the observations using the RATRAN radiative transfer code, we estimate outflow, infall, turbulent velocities, molecular abundances, and investigate any correlation with the evolutionary status of each source. The four sources (plus previously studied W43-MM1) have been ordered in terms of evolution based on their SED: NGC64334I(N)-W43-MM1-DR21(OH)-IRAS16272-4837-IRAS05358+3543. The molecular line profiles exhibit a broad component coming from the shocks along the cavity walls associated with the protostars, and an infalling (or expansion for IRAS05358+3543) and passively heated envelope component, with highly supersonic turbulence likely increasing with the distance from the center. Accretion rates between 6.3x10^-5^ and 5.6x10^-4^M_{sun}_/yr are derived from the infall observed in three of our sources. The outer water abundance is estimated to be at the typical value of a few 10^-8^ while the inner abundance varies from 1.7x10^-6^ to 1.4x10^-4^ with respect to H_2_ depending on the source. We confirm that regions of massive star formation are highly turbulent and that the turbulence likely increases in the envelope with the distance to the star. The inner abundances are lower than the expected 10^-4^ perhaps because our observed lines do not probe deep enough into the inner envelope, or because photodissociation through protostellar UV photons is more efficient than expected. We show that the higher the infall/expansion velocity in the protostellar envelope, the higher is the inner abundance, maybe indicating that larger infall/expansion velocities generate shocks that will sputter water from the ice mantles of dust grains in the inner region. High-velocity water must be formed in the gas-phase from shocked material.
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