Faraday rotation in clusters of galaxies

Faraday rotation in the clusters of galaxies are estimated systematically from the rotation measures of radio sources in or behind the clusters of galaxies. A cross-correlation of the Abell catalogue of rich clusters of galaxies with the catalogue of linear polarization of radio sources resulted in the identification of 10 clusters of galaxies. The average value of the rotation measures in the clusters of galaxies is about 20 rad m-2 and correspond to the well ordered magnetic field with the value of 2 x 10-7 gauss, if the electron densities is 10-4 cm-3. (author)