Observational Evidence of The Change of Activity Modes of Galactic Nuclei

Now there is no doubt that the activity of supermassive black holes in galactic nuclei has a transient character, and the total duration of the active phase is much shorter than the quiescent state. Even the term “archaeology of the active nucleus” has emerged. It implies the possibility of reconstructing the history of activity (changes in the ionising luminosity or power of a non-thermal radio source over time) by analysing how this activity expresses itself at galactic and extragalactic spatial scales (relic radio structures, gas clouds ’illuminated’ by ionising echoes, etc.). Increasing the number of such observations allowed us to identify objects where there is simultaneous evidence for switching between radiative (ionisation cones) and kinetic (radio jets) modes. In the classical unified scheme of galaxy activity, such behaviour is interpreted as a change from an Eddingtonian accretion rate to a less efficient accretion rate or vice versa. In this talk we consider specific examples of nearby (z less 0.3) active galaxies in which relic radio structures and damped ionisation cones are simultaneously observed.