Far-infrared CO and H2O emission in intermediate-mass protostars

Context. Intermediate-mass young stellar objects (YSOs) provide a link to understanding how feedback from shocks and UV radiation scales from low-to high-mass star forming regions. Aims. Our aim is to analyze excitation of CO and H2O in deeply embedded intermediate-mass YSOs and compare it with similar studies on low-mass and high-mass YSOs. Methods. Herschel/PACS spectral maps are analyzed for six YSOs with bolometric luminosities of L-bol similar to 10(2)-10(3) L-circle dot. The maps cover spatial scales of similar to 10(4) AU in several CO and H2O lines located in the similar to 55-210 mu m range. Results. Rotational diagrams of CO show two temperature components at T-rot similar to 320 K and T-rot similar to 700-800 K, comparable to lowand high-mass protostars probed at similar spatial scales. The diagrams for H2O show a single component at T-rot similar to 130 K, as seen in low-mass protostars, and about 100 K lower than in high-mass protostars. Since the uncertainties in T-rot are on the same order as the difference between the intermediate and high-mass protostars, we cannot conclude whether the change in rotational temperature occurs at a specific luminosity or whether the change is more gradual from low-to high-mass YSOs. Conclusions. Molecular excitation in intermediate-mass protostars is comparable to the central 10(3) AU of low-mass protostars and consistent within the uncertainties with the high-mass protostars probed at 3 x 10(3) AU scales, suggesting similar shock conditions in all those sources.