Some features in the spectra of extragalactic radio sources

The spectra of approximately 2000 sources in the Culgoora-3 list of radio sources were obtained by combining the 80 and 160 MHz flux densities from the Culgoora radio heliograph with other published flux data between 10 and 10,000 MHz. The data are considered very accurate and are used to study a spectral property which may indicate source evolution. Theories for a redshift-spectral index relationship, a radio power-spectral index relationship, and a linear dimension/spectral index correlation are presented. These three correlations are possibly due to a direct dependence of spectral index on redshift; thus an evolutionary origin is implied. If these relationships can not be proven, a reasonable interpretation of the results would be to implement a flattening of the electron energy spectrum with radio-galaxy age caused by repeated injections or reaccelerations of relativistic electrons over the 10 to the 10th years covered by the data.