Faraday Rotation Measures through the Cores of Southern Galaxy Clusters
  We present a study of the rotation measure (RM) obtained from a sample of extra-galactic radio sources either embedded in or seen in projection through a sample of seven southern galaxy clusters (declination less than 30 degrees). We compare our results with those obtained previously through similar statistical studies and conclude there is a statistically significant broadening of the RM signal in galaxy clusters when compared to a control sample. Further, we concur with the findings of Clarke (2000) that the typical influence of the cluster on the RM extends to around 800 kpc from the cluster core and that the RMs determined are on average consistent with a 1-2 micro G field. 
M. Johnston-Hollitt and R.D. Ekers