JET INTERACTION AND THE EVOLUTION OF COMPACT SYMMETRICAL RADIO-SOURCES

Readhead et al, have recently proposed that compact symmetric objects (CSOs) evolve into larger double sources many kiloparsecs in extent. T hey propose a detailed empirical model based on recent VLBI survey dat a that suggest a non-serf-similar evolution with a constant hot-spot a dvance speed independent of the ambient density. The implications of t his observational result are explored via numerical modeling. It is fo und that pure luminosity evolution with constant lobe advance speed is unlikely on the small scales of the CSOs if any ambient pas density g radients exist. However, the transition from CSO to larger double radi o sources may involve a nearly constant advance speed into a medium of decreasing density as suggested by Readhead et al. This result can be reproduced by inclusion of additional physics in non-self-similar flo ws, namely the losses experienced by the outflowing jet as it interact s with its surroundings. The data of Readhead et al. provide observati onal evidence that this interaction is an important feature of radio s ource evolution.