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During the formation of a star, material is ejected along powerful jets thatimpact the ambient material. This outflow phenomenon plays an important role inthe regulation of star formation. Understanding the associated shocks and theirenergetic effects is therefore essential to the study of star formation. Wepresent comparisons of shock models with observations of H$_2$ and SiO emissionin the bipolar outflow BHR71, and predict water emission, under the basicassumption that the emission regions of the considered species coincide, at theresolution of currently available observations. New SiO observations from APEXare presented, and combined with \textit{Spitzer} and ground-based observationsof H$_2$ to constrain shock models. The shock regions associated with targetedpositions in the molecular outflow are studied by means of a 1D code thatgenerates models of the propagation of stationary shock waves, andapproximations to non-stationary ones. The SiO emission in the inner part ofthe outflow is concentrated near the apex of the corresponding bow-shock thatis also seen in the pure rotational transitions of H$_2$. Simultaneousmodelling is possible for H$_2$ and SiO and leads to constraints on the siliconpre-shock distribution on the grain mantles and/or cores. The best-fittingmodels are found to be of the non-stationary type, but the degeneracy of thesolutions is still large. Pre-shock densities of 10$^4$ and 10$^5$ cm$^{-3}$are investigated, and the associated best-model candidates have rather lowvelocity (respectively, 20-30 and 10-15 km s$^{-1}$) and are not older than1000 years. We provide emission predictions for water, focusing on thebrightest transitions, to be observed with the PACS and HIFI instruments of the\textit{Herschel} Telescope.

Revisiting the shocks in BHR71: new observational constraints and H2O predictions for Herschel