The CO excitation diagram produced from our best-fit model (red squares). Two temperature components can be fitted to our shock model over the PACS range of observations: a warm component (T_ex = 216 K, dark blue line) fitting the level populations for J_up = 12 to 25 (light blue squares), and a hot component (T_ex = 422 K, light green line) fitting the level populations for J_up = 26 to 40 (dark green squares).