Observational evidence for the link between the variable optical continuum and the jet of a radio-loud galaxy 3C 390.3

Abstract

The ``central engine'' of AGN is thought to be powered by accretion on a central nucleus believed to be a super-massive black hole. The localization and exact mechanism of the energy release in AGN are still not well understood. We present observational evidence for the link between variability of the radio emission of the compact jet, optical and X-ray continua emission and ejections of new jet components in the radio galaxy 3C 390.3. The time delays between the light curves of the individual jet components and the light curve of the optical continuum are estimated by using minimization methods and the discret correlation function. We find that the variations of the optical continuum are correlated with radio emission from a stationary feature in the jet. This correlation indicates that the source of variable non-thermal continuum radiation is located in the innermost part of the relativistic jet. We suggest that the continuum emission from the jet and counterjet ionizes material in a subrelativistic outflow surrounding the jet, which results in a formation of two conical regions with broad emission lines (in addition to the conventional broad line region around the central nucleus) at a distance more or equal to 0.4 parsecs from the central engine. Implications for modeling of the broad-line regions are discussed.