Figure 9.
Free–free optical depth τν as a function of gas temperature T behind the shock. The optical depth is normalized to a fiducial value |$\tau _{0,\nu }\equiv (n_{4}/10^{7}{\rm cm^{-3}}) v_8/\nu _{10}^2$|. Different lines correspond to the cases calculated for a cooling function including full line cooling (purple) and one including just free–free cooling (green).