What have we learned about the life-cycle of radio AGN
Raffaella Morganti (Invited)
The recurrent activity of radio AGN, with phases of activity alternating to periods of quiescence, has been known since the early studies of these objects. However, the full relevance of this cycle has been only emphasised in the past years by the requirement, from the AGN feedback scenario, of a recurrent impact of the energy released by the SMBH during the lifetime of the host galaxy: only in this way AGN feedback can influence galaxy evolution. Timing the duty-cycle of radio AGN offers the possibility not only to quantify this impact but also to connect it with their evolutionary stage. Radio AGN in different evolutionary phases can be identified by their properties, like morphology and spectral indices. However, building large enough samples of radio sources in the most elusive phases of their evolution, like dying and restarted objects, has been always challenging. Only by characterising these phases, the full duty cycle can be quantified. The availability of the new, large surveys and, in particular, the one at low frequencies, together with the development of new numerical simulations, makes this task now possible. Indeed, the past years have brought particularly exciting results in this field. IN this talk I will give an overview of the work done so far, highlighting some of the results obtained using a variety of radio telescopes as well as the initial results from the comparison with the predictions from numerical simulations.