ABSTRACT:
Radio galaxies (RGs) are active galactic nuclei (AGN) able to launch relativistic jets, the most energetic phenomena in the Universe, which can have a large impact on galaxy evolution. Current high-sensitivity and high-resolution surveys have shed new light on properties of RGs, particularly in the local Universe (z<0.3) and at low luminosities (<10^24 W/Hz a 1.4 GHz), where the bulk of the AGN population was not much explored in opposition to the well-studied powerful extended RGs, FRI and FRII. A large population of compact RGs, named FR0s, which differ from classical FRI/IIs, by lacking large-scale (>10 kpc) jet emission, is emerging from recent studies and is revolutionising our idea of an ordinary RG. These sources show host and nuclear characteristics similar to those of FRI radio galaxies. However, in the radio band, while FR0s and FRIs share the same core properties, the kpc-scale diffuse component dominant in FRIs is missing in FR0s. I will present multi-band observations of FR0s, which probe different physical scales of the jet structures and help us to understand their actual capability of launching jets with respect to FRIs. High-resolution radio observations of a sample of FR0s provide evidence that parsec-scale jets in FR0s are mildly relativistic with a bulk velocity on the order of 0.5c or less. A jet structure with a thin inner relativistic spine surrounded by a low-velocity sheath, launched by a low-spinning black hole, could be in agreement with the observed multi-band FR0 properties.
Link alla videochiamata: https://meet.google.com/myc-hsgs-yik
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