Speaker
Description
Comparable energy contents of radio lobes in FR II sources calculated
using their luminosities and their confinement by external medium seem
to exclude possibility of their energy domination by protons.
This suggests that the jets powering the lobes are pair dominated.
Large pair content of jets is indicated also by blazar models, which
for the electron-proton plasma predict much larger jet powers than obtained
using energetics of their radio lobes.
However, noting the very efficient cooling of electrons/positrons in
blazars, the energy flux of jets at sub-parsec distances from a black hole is
expected to be dominated by protons and magnetic fields rather than by pairs.
Neglecting the leptonic contribution to the jet energy flux also at kpc scales
would imply very efficient conversion of kinetic energy of cold protons to
internal energy of electrons and positrons in terminal shocks. This however is
rather difficult to accomplish and, therefore, we propose that energetical
domination of pairs over protons is already achieved prior to the jet
termination. We investigate conditions required to form such hot,
pair-dominated jets and provide some additional observational and theoretical
arguments in favor of their existence.
