Dr. Alexander Plavin (Black Hole Initiative, Harvard University)

Active galaxies as particle accelerators: the multimessenger view

Astronomy has been solely relying on electromagnetic waves for centuries, until recent decades brought new messengers. These include high-energy neutrinos detected by specialized observatories – IceCube, KM3NeT, Baikal-GVD. Neutrinos have been associated with distant active galaxies, quasars, since 2017: initially in terms of individual objects, then with well-defined source samples. In this talk, I will present recent observational discoveries shedding light on neutrino origins in quasars. I'll discuss how they challenge the current models of quasars and particle acceleration in their centers. These objects appear to accelerate heavy particles even more efficiently than previously expected. Our understanding of cosmic particle accelerators still has many gaps, and I will outline how current and future instruments can fill them.