2-SIDED EJECTION IN POWERFUL RADIO-SOURCES - THE COMPACT SYMMETRICAL OBJECTS

We present VLBI images of the compact high-luminosity radio galaxy 235 2+495 that show symmetric structure on either side of a prominent cent ral core. This contrasts strongly with the asymmetric nuclear structur e exhibited by the great majority of powerful extragalactic sources. T he outer structure of 2352 + 495 takes the form of two ''mini-lobes'' containing hot spots; in this respect this compact radio galaxy resemb les extended radio galaxies, but its overall size, approximately 150 p c, is approximately 1000 times smaller. A reanalysis of existing data on the radio galaxy 0710+439 shows similar compact structure, and toge ther these VLBI images confirm the existence of a class of two-sided c ompact symmetric objects (CSOs). We show that, in contrast to nuclear radio sources in other powerful objects, the observed structure of CSO s is not dominated by relativistic beaming effects. It is likely that many objects previously classified as ''compact doubles'' will prove t o be CSOs when mapped with VLBI with high dynamic range.