Neutrino emission from Blazars.

During the last decade, multi-messenger astronomy has become increasingly relevant for the astrophysical community. In this context the discovery of PeV neutrinos by IceCube in 2012, in clear excess to the expected atmospheric flux at very-high energy (≳ 100 TeV ), marked the beginning of the high-energy neutrino astrophysics era. Differently from photons, neutrinos can carry information about the core of the astrophysical objects that produce them, giving us a better understanding of the internal composition of their sources. The origin of these neutrinos is still an open issue. Among the possible extragalactic neutrino sources, Blazars start to stand out. Blazars are associated to active galactic nuclei hosting a relativistic jet oriented close to our line of sight. The presence of jets and the strong non-thermal emission up to the TeV band makes them natural accelerators of particles. In September 2017 the spatial coincidence between a neutrino event detected by IceCube, with a good angular resolution, and a blazar, TXS 0506+056, was observed for the rst time. This event is even more intriguing because of the high-state emission in γ-ray band of this blazar. During the three years of my PhD, I focused my attention on the study of blazar objects as neutrino emitters. In this thesis all my work on this topic is presented.