Internal Faraday rotation effects in transparent synchrotron sources

Calculations of the polarization properties of transparent synchrotron sources subject to internal Faraday rotation are presented and discussed. Effects when sources are fully, partially, or not resolved are included. In particular, the characteristics of unresolved spherical and cylindrical sources are compared. In addition, the effects of partial resolution and inhomogeneity are considered for spherically symmetric sources. The calculations emphasize that accurate estimates of Faraday depth are difficult to make unless one is confident that the polarized emission and the Faraday dispersion are homogeneous within the source. To estimate correctly the intrinsic polarization direction when the source Faraday rotation is large, the source must be sufficiently resolved, so that there is little variation in Faraday depth across the telescope beam at any wavelength examined.