Linking low- to high-mass young stellar objects with

Context. Water probes the dynamics in young stellar objects (YSOs) effectively, especially shocks in molecular outflows. It is therefore a key molecule for exploring whether the physical properties of low-mass protostars can be extrapolated to massive YSOs, an important step in understanding the fundamental mechanisms regulating star formation. Aims. As part of the WISH key programme, we investigate excited water line properties as a function of source luminosity, in particular the dynamics and the excitation conditions of shocks along the outflow cavity wall. Methods. Velocity-resolved Herschel-HIFI spectra of the H2O 202–111 (988 GHz), 211–202 (752 GHz) and 312–303 (1097 GHz) lines were analysed, together with 12CO J = 10–9 and 16–15, for 52 YSOs with bolometric luminosities ranging from 105 L⊙. The H2O and 12CO line profiles were decomposed into multiple Gaussian components which are related to the different physical structures of the protostellar system. The non-LTE radiative transfer code rade