POLARIZATION PROPERTIES OF EXTRA-GALACTIC RADIO-SOURCES

In order to give a good description of the polarization properties of extragalactic radio sources together with some other radio and optical data for these sources, all published polarization observations of extragalactic radio sources from 1965 to the middle of 1974 have been collected. After applying selection criteria for inadequately observed sources and applying weighting procedures for different measurements at the same wavelength these data form a catalogue of 510 sources with a maximum of 120 entries per source. It is available on magtape (or cards...) from the Strasbourg Stellar Data Center. The catalogue is described in detail in a forthcoming publication (Eichendorf and Reinhardt, 1978a); details related to the catalogue as available from Strasbourg are given in Eichendorf and Reinhardt (1978b). The present paper contains the statistical and physical investigation of the data and their implications. Starting both from synchrotron radiation theory with a simple source models and from the observed spectral polarization it was possible to define a polarization index, called αp, the degree of polarization P(λ) being P~vαp. This αp is calculated in analogy to the spectral index and seems to give a good description of the spectral polarization of extragalactic radio sources. By use of either this polarization index or the spectral distribution of the flux densities significant differences between radio galaxies and quasars have been found (radio galaxies clearly show steeper spectra than quasars). For all the original, recalculated and derived data a statistical analysis has been performed. The results and conclusions from it are discussed. © 1979 D. Reidel Publishing Co.