Interferometric observations of compact components in extragalactic radio sources. II.

High-resolution observations of the brightness and polarization at wavelengths 18 and 31 cm of 18 double radio sources are presented. The sources are distant high-luminosity objects, with energy densities in the outer heads of typically 10 to the -9th J/cu m. From the depolarization rate, the electron density is deduced to be typically 1000 per cu m, and the sound speed is 0.05 c. The lifetime of the synchrotron electrons is usually shorter than the sound-crossing time, suggesting that reacceleration occurs throughout the emitting regions. In seven of the sources, the polarization is highly asymmetric, in most cases being virtually confined to one of the two components. The cause of this property (which does not appear to be general among a large sample of sources) is not clear.