RADIO-SOURCE ORIENTATION AND THE COSMOLOGICAL INTERPRETATION OF THE ANGULAR SIZE REDSHIFT RELATION FOR DOUBLE-LOBED QUASARS

The angular size-redshift test for quasars was compared with various cosmological models including non standard models. The possible effects of radio source orientation and relativistic beaming were taken into account in the analysis. It was found that orientation effects alone were not sufficient to explain the observed theta-z relation in terms of Friedmann models. In addition, linear size evolution of the form D approximately (1 + z)-n, with 0.75 less than or similar n less than or similar 1.2 would be required for 0 less than or similar OMEGA less than or similar 1.0, or possibly an inverse correlation between luminosity and linear size. The non-standard cosmological models all gave better fits to the deprojected data than the Friedmann models in the absence of evolutionary effects, with the tired light effect providing the best fit.