Infrared Space Observatory Spectroscopy of HH 7-11 flow and its redshiftedcounterpart

We have used the two spectrometers on the Infrared Space Observatory to obs erve the HH 7-11 flow, its redshifted counterpart, and the candidate exciti ng source SVS 13 in the star formation region NGC 1333. We detect atomic ([ O I] 63 mu m, [O I] 145 mu m, [Si II] 34.8 mu m, [C II] 158 mu m) and molec ular (H-2, CO, H2O) lines at various positions along the bipolar flow. Most of the observed lines can be explained in terms of shock-excited emission. In particular, our analysis shows that dissociative (J-type) and nondissoc iative (C-type) shocks are simultaneously present everywhere along both lob es of the flow. We confirm the low-excitation nature of the Herbig-Haro neb ulosities, with shock velocities v(s) less than or similar to d 40-50 km s( -1). Toward both lobes of the outflow, we find preshock densities of n(0) s imilar to 10(4) cm(-3) for both the J and C components, implying B-0 simila r to 100 mu G for B-0 proportional to n(0)(0.5). In the central region of t he flow, close to the exciting source, the preshock density deduced for the C-shock component is n(0) similar to 10(5) cm(-3), suggesting a magnetic h eld similar to 3 times stronger. We propose that the deficiency of gas-phas e water in the post-C-shock regions is caused by freezing onto warm grains processed through the J-shock front and traveling along the magnetic field lines. The total observed cooling from the dissociative shock components is consistent with the power lost by a slow molecular out flow accelerated by a fast neutral HI wind. Finally, the skin of the cloud seen in projection toward the how appears to be weakly photoionized by ED +30 degrees 549, the dominant illuminating source of the NGC 1333 reflection nebula.