Hydrodynamic models of Herbig–Haro objects

Two-dimensional cylindrical hydrodynamic models of neutral and collisionally ionized stellar wind–cloudlet interactions are calculated as possible models for H–H objects. For neutral winds, shocks propagate into the cloudlet and its shape is distorted and displaced in the direction of the wind. For hot ionized winds interacting with spherical mass concentrations a bow shock is formed, but the highest temperatures and largest ionization fraction occurs on the lee side of the cloudlet. Winds interacting with a neutral globule imbedded near the ionized surface of an elongated cloud produce the largest ionization at the cloud face presented to the wind and have a gradient in ion density from the face nearest the symmetry axis along the cloud surface. Cavities in the cloudlet surface facing the winds cause ‘hotspots’ having temperatures ∼ 105 K.