Study of the brightness and polarization structure of extragalactic radio sources

We have determined the brightness and linear polarization structure of 19 extended extragalactic radio sources at a frequency of 10.7 GHz and with a synthesized beam 17times17 arcsec csc delta. Compact components with self-absorption spectra coincident with the nucleus of an associated galaxy are fairly common, while many sources display regions of high percentage polarization, sometimes greater than 40%. Comparison of our results with other studies, all at lower frequencies (generally less than or equal to5 GHz), has yielded information on spectra, depolarization rates, and Faraday rotation of the polarization plane in various source regions. We can identify at least four distinct classes of extragalactic radio source. These classes form a sequence along which the prominence of the compact central component declines relative to that of the extended outer regions, while those outer regions become more ordered in their structure and assume specific polarization characteristics. We speculate that this sequence is in fact an evolutionary sequence. (auth)