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 λ 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 λ Edd in our sample is distributed within a narrow range λ Edd ∼ 0.01-0.2; (ii) the normalized jet power P j/L Edd formally correlates with the accretion rate λ Edd, with some saturation at the largest values λ Edd > 0.05; (iii) the jet production efficiency spans a range from η jet ≲ 10-3 up 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 η jet on the hardness-intensity diagram L X/L bol-λ Edd, with the jets being produced most efficiently during the high/hard states, and suppressed during the soft states.