The gravitational slingshot and the structure of extragalactic radio sources

We propose a simple dynamical mechanism to eject massive objects from the nuclei of galaxies. When three or more massive objects near the center interact strongly, the configuration becomes gravitationally unstable and splits up. In the case of three objects, two of them will usually form a compact binary and fling out the third. The recoil momentum can eject the binary from the galaxy in the opposite direction. To study the interaction for a large range of initial conditions, we have numerically computed the orbits of 25,000 triple systems and of 250 two-binary systems. Their general properties are analyzed and compared with the observed structures of extragalactic radio sources. The double nature of many radio sources, their association with the plane of a central elliptical galaxy, the presence of very compact radio components, and a number of other observed properties are readily related to the gravitational slingshot. We also discuss observational constraints on radio emission from the massive objects, and further observations of special interest. Subject headings: celestial mechanics - galactic nuclei - galactic structure - radio sources