DEPOLARIZING HOT GAS IN CLUSTERS OF GALAXIES WITH A STRONG DOUBLE RADIO-SOURCE

Polarization data of strong double-lobed radio sources with one jet and X-ray data are combined to determine the magnetoionic properties of the medium causing asymmetric depolarization. We find that the effect is probably due to the intracluster medium (ICM) as a turbulent Faraday screen. For five sources (3C 9, 4C 01.11, 3C 270.1, 3C 275.1, 3C 208), we determine the coherence length of the magnetic field to be in the range of 1-4 kpc. The EINSTEIN fluxes give upper limits for the core electron densities of 2-7 × 10-3 cm-3, since part of the X-ray emission may be produced by an active nucleus. We therefore get lower limits on the magnetic field strength of 3-8 μG. The ratio of thermal to magnetic pressure has an upper limit of 60-400. The results are based on a simple model for the propagation of synchrotron radiation in a magnetic field configuration that consists of randomly oriented cells. The transport equation for the mean intensity is solved in terms of angle-averaged emission and absorption coefficients. The rms-deviations of the intensity, polarization, and Faraday rotation from their respective mean values reduce as the inverse square root of the number of cells along and/or across the line of sight. It is further shown that modifications for other spectra of cell sizes yield only a factor of order unity.