The physical structure of radio galaxies explored with three-dimensional
  simulations
  We present a large systematic study of hydrodynamic simulations of supersonic
adiabatic jets in three dimensions to provide a definitive set of results on
exploring jet density, Mach number and precession angle as variables. We
restrict the set-up to non-relativistic pressure-equilibrium flows into a
homogeneous environment. We first focus on the distribution and evolution of
physical parameters associated with radio galaxies. We find that the jet
density has limited influence on the structure for a given jet Mach number. The
speed of advance varies by a small factor for jet densities between 0.1 and
0.0001 of the ambient density while the cocoon and cavity evolution change from
narrow pressure balanced to wide over-pressure as the ratio falls. We also find
that the fraction of energy transferred to the ambient medium increases with
decreasing jet-ambient density ratio, reaching approx 80%. This energy is
predominantly in thermal energy with almost all the remainder in ambient
kinetic form. The total energy remaining in the lobe is typically under 5\%. We
find that radio galaxies with wide transverse cocoons can be generated through
slow precession at low Mach numbers. We explore a slow precession model in
which the jet direction changes very slowly relative to the jet flow dynamical
time. This reveals two separated bow shocks propagating into the ambient
medium, one associated with the entire lobe expansion and the other with the
immediate impact zone. The lobes generated are generally consistent with
observations, displaying straight jets but asymmetric lobes.
