RM catalogue of the Chandra Planck clusters

Faraday rotation and depolarisation of extragalactic radio sources are useful probes, but the limited availability of polarised radio sources necessitates the stacking of clusters to study average magnetic field properties. We recently presented a Karl G. Jansky Very Large Array survey of the 124 most massive Planck clusters at low redshift (z<0.35), finding a clear depolarisation trend with the cluster impact parameter, with sources at smaller projected distances to the cluster centre showing more depolarisation.

In this study, we combine the depolarisation information with the observed rotation measure (RM) and present an investigation of the average magnetic field properties of the sample, using both background sources and sources embedded in clusters. We observe a significant increase in the RM scatter, {sigma}_RRM_, closer to the cluster centres. Averaging all 124 clusters, we find a scatter within R500 of {sigma}_RRM_=209+/-37rad/m^2^, with background sources and cluster members showing similar values (200+/-33 and 219+/-66rad/m^2^, respectively).