Optical-radio mapping: The kinetic efficiency of radio-loud AGNS

We constrain the mean kinetic efficiency of radio-loud active galactic nuclei by using an optically selected sample for which both the optical and the radio luminosity functions (LFs) have been determined; the former traces the bolometric luminosity L, while the latter traces the kinetic power L-k, empirically correlated to the radio emission. Thus in terms of the ratio g(k) L-k/L, we can convert the optical LF of the sample into a radio one. This computed LF is shown to match the directly observed LF for the same sample if g(k) = 0.10(-0.01)(+0.05) holds, with a scatter sigma = 0: 38(-0.09)(+0.04) dex; with these values we also match a number of independent correlations between Lk; L and radio emission, that we derive through Monte Carlo simulations. We proceed to translate the value of gk into a constraint on the kinetic efficiency for the production of radio jets or winds, namely, epsilon(k) = L-k/M(a)c(2) similar to 0.01 in terms of the rate. M-a of mass accretion onto the central black hole. Then, on assuming that on average the radio sources share the same kinetic efficiency, we compute a solid lower limit of about 25% on the contribution of radio sources to the local black hole mass density.