Compact components in a complete sample of extragalactic radio sources

A statistically complete sample of 100 extragalactic sources stronger than 2 Jy at 1400 MHz was observed on a 3.5x106 wavelength baseline at 430 MHz. The unresolved pulsar AP2016 was used to normalize the fringe visibilities, with the result that all extragalactic sources appear at least partially resolved. In general, sources with flat spectra (α<+0.5) show fringes, while steep-spectrum sources do not, confirming that flat spectra are produced by synchrotron self-absorption rather than unusual electron-energy distributions. The spectral index-luminosity relation for radio galaxies is shown to reflect differing electron-energy distributions rather than self-absorption. Nearly all quasars, even those with steep spectra, contain components brighter than 1010 K. Purely radio ''identifications,'' made by calling fully resolved sources galaxies and sources showing fringes quasars, agree with 80 percent of the available optical identifications