Radiative bow shock models of Herbig-Haro objects

The authors have constructed bow shock models of HH objects from a collection of 43 radiative planar shock models. The bow shock models are used to predict the line ratios and line profiles expected from HH objects, and comparison of the model with four different regions containing HH objects indicates that a single unifying model - a radiating bow shock formed around a "bullet" of dense gas plowing into the ambient medium - can account for the bulk of the existing observations. Spectral line profiles expected from stationary cloudlets and moving bullets are discussed for a variety of shock velocities, orientation angles, and emission lines. It is shown that such models provide a natural explanation for the spectra of HH 32 and the HH objects in Cepheus A.