Compact Features in a Complete Sample of Radio Sources

The occurrence of compact features in a complete sample of 3CR sources, as revealed by interplanetary scintillation at 81·5 MHz, is described. It is found that ‘ hot spots ’ having a typical size of 5 kpc commonly exist in sources of high luminosity. Hot spots account for at least half the total radiation in many high luminosity sources when the overall extent of the source is around 100 kpc. Sources having an extent exceeding about 200 kpc do not usually contain prominent hot spots and are of lower luminosity. The significance of these facts is discussed in relation to the beam model of extragalactic radio sources