The FR0 population: Unveiling the Most Abundant Radio Galaxies in the Local Universe

Radio galaxies (RGs) are the primary laboratories for studying relativistic jets, the most energetic phenomena in the Universe, and their subsequent feedback on host galaxy evolution. While classical Fanaroff-Riley (FRI and FRII) sources have historically defined our understanding of these systems, recent high-sensitivity radio and optical surveys in the local Universe (z less than 0.3) have revealed that the bulk of the population consists of compact radio galaxies, named FR0s. These sources are characterized by a lack of large-scale (10 kpc and more) diffuse emission, despite possessing nuclear properties nearly identical to their more powerful FRI cousins.

I will present multi-band observations of FR0s probing different physical scales of the jet structures that help us to understand their actual capability of launching jets with respect to FRIs. To reconcile their multi-band characteristics, I will propose an accretion-ejection model, featuring mildly-relativistic jets powered by a low-accreting low-spinning black hole. Finally, I will discuss the implications of these compact structures for AGN feedback, questioning whether the modest scales of FR0 jets can still significantly influence the interstellar medium of their host galaxies and their evolution. In the near future, the Square Kilometre Array (SKA) with its high sensitivity and angular resolution will finally determine whether FR0s represent a distinct evolutionary stage or a fundamentally different mode of black hole accretion-ejection in RG population.

Dr. Ranieri Diego Baldi, Istituto di Radioastronomia di Bologna (IRA, INAF)

After receiving his PhD degree in 2010 at the University of Turin, he was a postdoctoral fellow at the Space Telescope Science Institute of Baltimore (USA) between 2010 and 2011, then moving to SISSA (Trieste) in 2011, to the Technion Institute of Haifa (Israel) in 2013, and finally at the University of Southampton (UK) in 2015. From 2020 on, Dr. Ranieri Diego Baldi is a permanent researcher at INAF-IRA in Bologna.