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

Abstract

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