High-Resolution Interferometry of Small Radio Sources Using Intercontinental Base Lines

Radio telescopes located near Green Bank, West Virginia, and Onsala, Sweden, have been used as elements of an interferometer with a base line of 6319 km. Observations at 18 cm (35 X 106 X base line) and at 6 cm (105 X 10~ X base line) show that a number of radio galaxies and quasi-stellar sources con- tain components with angular dimensions of the order of O'OOl or less. In two Seyfert galaxies, the upper limits to the sizes of regions of time-varying emission indicate that the sources do not expand with extreme relativistic velocities in the manner suggested by Rees and Simon