Some evolutionary characteristics of radio galaxies with double structures

In this paper a statistical investigation has been made on some characteristics of the evolution of radio galaxies with double structure. 77 radio galaxies with known redshifts are selected. The main results are as follows: 1. In the angular size-redshift diagram, there appears to be a lower bound (θ_min −z), which corresponds to a minimum linear size $\text{D}{}_{\mathrm{<mtext>min</mtext>}}\text{⋍ 40}\text{kpc}$. It looks as though all double structures are initially formed with this size. 2. The radio luminosity (L), volume (V) and total energy (E) of individual components vary with the linear separation D. There may be a critical separation $\text{D}{}_{\mathrm{c}}\text{⋍ 600}\text{kpc}$ such that when D < D_c, L, V and E increase steadily with the increasing D; while for D > D _c, L, V and E remain essentially constant. Somewhat unexpectedly, there seems to be no correlation between E/V (or L/V) and D. 3. Among radio galaxies with the largest linear size, the absolute visual magnitudes appear to get fainter with increasing D at the rate of about +4.8^m/Mpc.