Optical emission from shocks. V. The Magellantic Cloud supernova remnants

High-resolution ΔVapprox. =25 km s-1 velocity data on Magellanic Cloud supernova remnants (SNRs) in the [O II] doublet obtained with the 3.9 m Anglo-Australian telescope combined with absolute Hα photometry obtained with the 1 m telescope at Siding Spring have been shown to be inconsistent with any model requiring the interstellar medium to be homogeneous about, or smoothly varying away from, the explosion center. However, the data do give very strong support to the cloudlet shock model put forward by McKee and co-workers. The cloudlets have a mean density around 12 cm-3 and are generally less than a parsec across. The mean kinetic energy deposited by the supernova is 51.3 > or approx. = logE > or approx. = 50.3, with a probable value near 7 x 1050 ergs