INVESTIGATING THE FARADAY ROTATION MORPHOLOGIES OF CIRCUMSTELLAR AND INTERSTELLAR BUBBLES

We compute model polarization position angle maps for the effect of Faraday rotation for circum-stellar and interstellar bubbles. In the circumstellar case, we consider spherically symmetric bubbles, as examples of wind-blown bubbles, with either azimuthal or split monopole magnetic fields. In the case of an azimuthal field, the polarization position angle maps are antisymmetric about the field axis, because Faraday rotation is sensitive to whether the line-of-sight magnetic field points toward or away from the observer. By contrast a split monopole field produces a map of only one sign for the polar-ization position angle. We also consider Faraday rotation as a probe of an interstellar magnetic field. In this case a supernova explosion is considered to provide an ionization front that moves through the interstellar medium. We explore how a turbulent magnetic field affects the polarization position angle maps. Our results indicate that it is mainly the largest turbulent scales that are relevant for Faraday rotation. Subject headings: ISM: Faraday rotation, —supernovae: early-type stars radio polarization 1