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Session 106 - Clusters of Galaxies.
Display session, Saturday, January 10
Exhibit Hall,
Magnetic fields are present and, in general, dynamically important over a wide range of astronomical scales. On the scale of clusters of galaxies, their presence is indicated by the radio signatures of diffuse cluster- wide synchrotron halos, and Faraday rotation of the polarized radio sources located within and behind the central regions of the clusters. Such magnetic fields, while poorly understood, may prove to be dynamically important to the cluster. The fields will confine cosmic rays within the cluster and suppress thermal conduction within the ICM (possibly leading to the formation of cooling flows).
We examine the Faraday rotation of radio sources to statistically investigate the magnetic field strength and radial extent within the intracluster medium. The cluster sample was selected by cross correlating strong ROSAT clusters with the polarized radio sources in the NRAO VLA Sky Survey (NVSS). We obtained follow-up polarimetry at the VLA of all NVSS sources in four to six additional wavelengths for two sets of sources. The first set of sources is located (in projection) behind the intracluster medium and the second set consists of control sources located further from the cluster center. The rotation measure data from these sources, together with the ROSAT electron density profiles, will provide us with a measure of the cluster's magnetic field strength. We will present our cluster sample and the initial results from our analysis in this poster.
