The angular size-redshift relation and the unified scheme for radio-loud quasars

The unified scheme in which the observed differences in the radio properties of the two classes of radio-loud quasars; the core- and lobe-dominated quasars (CDQs and LDQs) arise because they are seen at different angles to the line of sight has been investigated using the observed median angular size-redshift (theta - z) relation for two well defined samples. It is shown that the median angular size of LDQs exceeded that of CDQs by a factor of similar to 3 in any given redshift bin. This is qualitatively in agreement with the unified scheme in which the radio axes of CDQs are closer to the line of sight than those of LDQs.