Magnetic Fields in Clusters: Faraday Rotation in A400 and A2634

We present Faraday rotation data for radio sources in the centers of the Abell clusters A400 and A2634. These clusters do not contain strong cooling cores, while they do contain large (>100 kpc), tailed radio sources. Thus, our data extend previous work on rotation measure in cluster centers, to lower density cores, and larger scales.

We find the rotation measure, and thus the magnetic field, is ordered on scales ~10-20 kpc in both clusters; and its geometry appears to be determined by the distribution of the X-ray emitting gas, rather than by the radio tails.

We also find the magnetic fields in these clusters are dynamically important, We suggest that these as well as previous cluster-center Faraday data are measuring magnetic fields in the intracluster medium, rather than in a skin of the radio source.

Ap.J., to appear, 2002. full ps file; figure 1; figure 2; figure 3; figure 4; figure 5; figure 6; figure 7; figure 8; figure 9; figure 10;
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