Structure of a Radiative Shock

The structure of a radiative shock. Material enters the shock front at left with a velocity V and is slowed by a factor of 4 after crossing the shock. The density jumps by a factor of 4 at the shock and increases gradually as the gas cools and slows. As an example, cooling zones of oxygen are depicted by the x's, circles and dots. This diagram is drawn in the frame of reference of the shock - for HH objects viewed from the star all components of this diagram would appear to move to the right at a velocity 10V - 20V.