The Dynamic Evolution of Young Extragalactic Radio Sources
  The evolution of symmetric extragalactic radio sources can be characterized
by four distinct growth stages of the radio luminosity versus size of the
source. The interaction of the jet with the ambient medium results in the
formation and evolution of sources with non-standard (flaring) morphology. In
addition, cessation or restarting of the jet power and obstruction of the jet
will also result in distinct morphological structures. The radio source
population may thus be classified in morphological types that indicate the
prevailing physical processes. Compact symmetric objects (CSOs) occupy the
earliest evolutionary phase of symmetric radio sources and their dynamical
behavior is fundamental for any further evolution. Analysis of CSO dynamics is
presented for a sample of 24 CSOs with known redshift and hotspot separation
velocity and with a large range of radio power. Observables such as radio
power, separation between two hotspots, hotspot separation velocity, and
kinematic age of the source are found to be generally consistent with the
self-similar predictions for individual sources that reflect the varying
density structure of the ambient interstellar medium. Individual sources behave
different from the group as a whole. The age and size statistics confirm that a
large fraction of CSOs does not evolve into extended doubles.
