Giant radio galaxies via inverse Compton weakened jets

Abstract

Both analytical and numerical models for the propagation of relativistic jets through a hot interstellar medium (ISM) and into an even hotter intergalactic medium (IGM) have been considered. Earlier work allowed us to explain: the current mean linear-size of double radio sources (∼350 kpc); the decrease in linear-size with cosmological redshift, z; and, the increase in linear-size with radio power (at fixed z). We now have extended our models to allow for intrinsically extremely powerful jets, which may start off advancing relativistically through the interstellar medium. Eventually the energy density in the lobes becomes comparable to that of the microwave background, and inverse Compton losses of the synchrotron emitting electrons against the background photons become important. We argue that only powerful radio engines are responsible for giant radio galaxies (GRGs, those whose linear size exceeds 1.5 Mpc) and we can also explain most of the observed peculiarities of the GRGs, such as their rarity, moderate radio flux and relatively strong radio cores.