On the Jet Production Efficiency in a Sample of the Youngest Radio Galaxies

Here we discuss the jet production efficiency in a sample of 17 young radio galaxies with measured redshifts, kinematic ages, and nuclear X-ray fluxes, for which the observed luminosities of compact jets/lobes and accretion disks correspond to the same episode of AGN activity. For the targets, we analyze the available optical data, estimating the bolometric luminosities of the accretion disks L-bol, and the black hole masses; we also derive the minimum jet kinetic luminosities, P-j. With this information we investigate the distribution of our sample in the three-dimensional space of the accretion rate lambda(Edd) L-bol/L-Edd, the nuclear X-ray luminosity L-X considered here as a limit for the emission of the disk coronae, and P-j, expressing the latter two parameters either in the Eddington units, or in the units of the disk luminosity. We find that (i) the accretion rate lambda(Edd) in our sample is distributed within a narrow range lambda(Edd) similar to 0.01-0.2; (ii) the normalized jet power P-j/L-Edd formally correlates with the accretion rate lambda(Edd), with some saturation at the largest values lambda(Edd) > 0.05; (iii) the jet production efficiency eta(jet) less than or similar to 10(-3) up to similar to 0.2 at maximum, which is below the level expected for magnetically arrested disks around maximally spinning black holes; and (iv) there is a diversification in eta(jet) on the hardness-intensity diagram L-X/L-bol - lambda(Edd), with the jets being produced most efficiently during the high/hard states, and suppressed during the soft states.