Evolution of extended extragalactic double radio sources

A comparison of the flux density ratios s of the two components of extragalactic double radio sources and the ratios r of their angular separations from the associated optical object has been made for the Ooty occultation and 3CR samples. No marked variation is seen in the statistical properties of r & s over a range of flux densities exceeding 10 to 1. The distribution of r indicates an average velocity of separation of the two components from the parent object of less than about 0.2c. Simultaneous consideration of the r & s distributions indicates in addition a rapid evolution of the luminosity of radio components with age. Alternatively, the observations can be explained by assuming a nonuniform intergalactic medium with density variations of about a factor of 2 over scales exceeding several tens of kpc.