AN ATLAS OF THE INTERSTELLAR ENVIRONMENT OF WOLF-RAYET STARS IN THE MAGELLANIC CLOUDS

We have made a complete study of the interstellar environment around the Wolf-Rayet stars in the Magellanic Clouds. We present, in the form of an atlas, the results of a complete imaging survey in Halpha and of an extensive survey in the [O III] lambda5007 emission line, As a result of this survey, we have more than doubled the total number of ring nebulae known. These include cases of both rings of stellar ejecta and ring nebulae resulting from the sweeping up of the surrounding interstellar medium. We find that 34% of WN3-WN4 stars, 36% of late WN types, and 26% of WC4-WC5 stars are associated with a ring nebula of some kind. These figures are very similar to the percentage of Wolf-Rayet stars having ring nebulae in the solar neighborhood. The size distribution of ring nebulae is also similar. From the fact that the majority of Wolf-Rayet stars do not show ring nebulae, it is clear that mass loss in earlier phases of evolution, and the collective effects of the energy input from the clusters of OB stars with which the Wolf-Rayet stars are frequently associated, has profoundly modified the preexisting circumstellar environment. However, on the basis of statistics, we cannot exclude the possibility that all Wolf-Rayet stars have possessed a ring nebula at some stage in their evolution.