The estimate of kinetic powers of jets in FRII radio galaxies: existence of invisible components?

TL;DR

This study estimates the kinetic powers and ages of jets in FR II radio galaxies, revealing that most of the cocoon energy is likely carried by invisible components like thermal leptons or protons, with some jets possibly exceeding the Eddington luminosity.

Contribution

It provides new estimates of jet kinetic powers and cocoon energies, suggesting the presence of significant invisible components and potential super-Eddington accretion in FR II radio galaxies.

Findings

Large fractions of jet power are comparable to or exceed Eddington luminosity.

Cocoon energy exceeds minimum energy estimates, indicating hidden energy components.

Evidence for super-Eddington accretion in some sources.

Abstract

We investigate the total kinetic powers (L_j) and ages (t_age) of powerful jets in FR II radio galaxies by comparison of the dynamical model of expanding cocoons with observations. We select four FR II radio sources (Cygnus A, 3C 223, 3C 284, and 3C 219), for which the mass-density profiles of intracluster medium (ICM) are known in the literature. It is found that large fractions > 0.02 - 0.7 of the Eddington luminosity (L_Edd) are carried away as a kinetic power of jet. The upper limit of estimated 2 L_j / L_Edd are larger than unity (< 10) for some sources, suggesting a possibility of super-Eddington mass accretions. As a consequence of the large powers, we also find that the total energy stored in the cocoon (E_c) exceeds the energy derived from the minimum energy condition for the energy of radiating non-thermal electrons and magnetic fields (E_min): 4< E_c /E_min <310. This implies that most of the energy in cocoon is carried by invisible components such as thermal leptons (electron and positron) and/or protons.