The median angular sizes in different redshift bins were plotted as a function of (1+z) for bright steep spectrum radio galaxies and quasars, both together and separately. These were compared to the theoretical curves for an Euclidean universe, and for a Friedmann universe with linear size evolution of the forml(1+z)–x withx=3.It was found that for the sources as a whole, the variation of angular diameter with redshift behaved as expected in an Euclidean universe, which can also correspond to a Friedmann universe with linear size evolution and 1xz. There was a trend for the sources at low redshift (z0.6) to exhibit steeper linear size evolution withx3. However, if this trend should continue to higher redshifts, this would imply that the linear sizes of radio galaxies and quasars evolve differently with quasars evolving less strongly than radio galaxies.
Astrophysics and Space Science 11/1989; 162(2):343-347. DOI:10.1007/BF00640749