Timing the cycle of life and death of radio galaxies using LOFAR

Radio galaxies dominate the sky at radio wavelengths and represent an essential piece in the galaxy evolution puzzle.
The outbursts associated with radio galaxies can prevent hot gas from cooling and forming stars, thereby affecting the growth of the supermassive black hole and the host galaxy. However, they are fully effective only if they are recurrent in the life of the host galaxy.

This relevance of the recurrent radio activity means that studying the quiescent and active phases, i.e. the duty cycle, is crucial for our understanding of the origin of the feedback, its role in galaxy evolution, and the overall evolution of galaxies through cosmic time.

In this thesis, we study the life-cycle of radio galaxies by obtaining statistical samples of galaxies in different phases and by studying their multiwavelength properties. The ultimate goals are to understand the cause of the change in the activity of the central AGN, on which time scales these different phases occur, and the role of radio galaxies in our Universe. The research presented in this thesis was possible thanks to the LOw Frequency ARray (LOFAR) data in combination with the radio data at higher frequencies and ancillary data at different wavelengths. This combination of the multifrequency data allows for the construction of the bigger picture and a deeper understanding of the current questions related to the role of radio galaxies in our Universe.