Giant Radio Sources in View of the Dynamical Evolution of FRII-type Population. I. The Observational Data and Basic Physical Parameters of Sources Derived from the Analytical Model

The time evolution of giant lobe-dominated radio galaxies (with projected linear size D>1 Mpc if H0=50 km/s Mpc and q0=0.5) is analyzed on the basis of dynamical evolution of the entire FRII-type population. Two basic physical parameters, namely the jet power Q0 and central density of the galaxy nucleus ρ0 are derived for a sample of giants with synchrotron ages reliably determined, and compared with the relevant parameters in a comparison sample of normal-size sources consisting of 3C, B2, and other sources. Having the apparent radio luminosity P and linear size D of each sample source, Q0 and ρ0 are obtained by fitting the dynamical model of Kaiser et al. We find that: (i) There is no unique factor governing the source size. The sources are old, with temperate jet power (Q0) and are evolved in a relatively low-density environment (ρ0). The size is dependent, in order of decreasing partial correlation coefficients, on age, then on Q0, next on ρ0. (ii) A self-similar expansion of the sources' cocoon seems to be feasible if the power supplied by the jets is a few orders of magnitude above the minimum-energy value. In other cases the expansion can only initially be self-similar, a departure from self-similarity for large and old sources is justified by observational data of giant sources. (iii) An apparent increase of the lowest internal pressure value observed within the largest sources' cocoon with redshift is obscured by the intrinsic dependence of their size on age and the age on redshift, which hinders us from making definite conclusions about a cosmological evolution of intergalactic medium (IGM) pressure.