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The energetic composition of radio lobes in the FR II galaxies $-$ estimated by comparing their radio luminosities with the powers required to inflate cavities in the external medium $-$ seems to exclude the possibility of their energetic domination by protons. Furthermore, if the jets were dominated by the kinetic energy of cold protons, it would be difficult to efficiently accelerate leptons in the jets terminal shocks. Assuming that the relative energy contents of leptons, protons and magnetic fields are preserved across the shocks, the above implies that the large-scale jets should also be energetically dominated by leptons: $P_{rm e,j} gtrsim P_{rm p,j}$. On the other hand, previous studies of small-scale jets in blazars and radio cores suggest a pair content (number of electrons and positrons per proton) of the order of $n_{rm e}/n_{rm p} sim 20$. Assuming further that the particle composition of jets does not evolve beyond the blazar scales, we show that this implies an average random Lorentz factor of leptons in large-scale jets of $bargamma_{rm e,j} gtrsim 70(1+chi_{rm p})(20n_{rm p}/n_{rm e})$, and that the protons should be mildly relativistic with $chi_{rm p} equiv (epsilon_{rm p} + p_{rm p})/rho_{rm p} c^2 lesssim 2$, $p_{rm p}$ the pressure of protons, $epsilon_{rm p}$ the internal energy density of protons, and $rho_{rm p} c^2$ the rest-mass energy density of protons. We derive the necessary conditions for loading the inner jets by electron-positron pairs and proton-electron plasma, and provide arguments that heating of leptons in jets is dominated by magnetic reconnection.
Jet powers in many radio galaxies with extended radio structures appear to exceed their associated accretion luminosities. In systems with very low accretion rates, this is likely due to the very low accretion luminosities resulting from radiatively
We built a catalog of 122 FR~II radio galaxies, called FRII{sl{CAT}}, selected from a published sample obtained by combining observations from the NVSS, FIRST, and SDSS surveys. The catalog includes sources with redshift $leq 0.15$, an edge-brightene
We study the structures of ultra-relativistic jets injected into the intracluster medium (ICM) and the associated flow dynamics, such as shocks, velocity shear, and turbulence, through three-dimensional relativistic hydrodynamic (RHD) simulations. To
Using the photometric data on FR II radio galaxies obtained in the Big Trio Program and data from other sources, we confirmed the stable correlation between the spectroscopic and photometric redshifts up to z~4 determined from the evolutionary synthe
We report X-ray imaging of the powerful FR-II radio galaxy 3C353 using the Chandra X-ray Observatory. 3C353s two 4-wide and 2-long jets allow us to study in detail the internal structure of the large-scale relativistic outflows at both radio and X-ra