None of these shocks can become fully radiative within this timescale. In the 600yr available, the 300km/s shock cools from $T_e=1.27\times 10^6$K to $T_e=6.06\times 10^5$K; the 350km/s shock from $T_e=1.72\times 10^6$K to $T_e=1.43\times 10^6$K and the 400km/s shock from $T_e=2.25\times 10^6$K to $T_e=2.07\times 10^6$K.

The optical spectra of these shocks only contain emission lines of hydrogen and helium, as well as lines of coronal species of S, Si, Ar, Fe and Ni. The 300km/s shock is too slow to reproduce the observed \[\]/\[\] ratio, while the 400km/s overproduces \[\] relative to \[\], and is somewhat too faint relative to the cloud shock and its precursor. The curves on Figure \[fig12\] are presented for the 350km/s shock. In this figure, we added the contribution of the fast shock to that of the cloud shock, assuming that the fast shock covers an area of either 3 times, or 10 times that of the cloud shock. We assume that dust has been fully destroyed by shattering and sputtering in these fast shocks. Adding this fast shock contribution, we now achieve a satisfactory fit with the observational diagnostics for both \[\] and \[\].

The WiFeS images of N132D support the hypothesis that the faster 