Matthias Kadler | Radio-Astronomical Probes of High-Energy Processes in Relativistic Jets

Friday 22 Sept 2023, 10:00 → 12:00 Europe/Berlin

SR 05 (Villa)

Relativistic jets in active galaxies are key to scientific advance in a multitude of interrelated fields of modern astrophysics ranging from fundamental physics in strong gravity near supermassive black holes over astroparticle physics to feedback on cosmological scales. Advances in radio astronomy provide unique observational data on jets across scales, methods and disciplines.
In this talk, I will focus on relativistic jets in active galaxies as sites of extreme particle acceleration, which are the likely origin of very high-energy neutrinos and ultrahigh-energy cosmic rays. High-resolution Very-Long-Baseline Interferometric (VLBI) observations along with variability and polarimetric radio data provide crucial observational input to constrain theoretical/numerical models of the underlying physical processes and address many burning questions and riddles such as the infamous Doppler crisis, the unknown localization of the (very-high-energy) gamma-emission sites and the processes leading to neutrino and cosmic-ray emission. Observational challenges in the past have been imposed by the faint radio emission of important source classes like extreme high-synchrotron-peaked BL Lac objects. Thanks to new high-sensitivity VLBI and high-frequency single-dish total-intensity and polarimetric receiver systems, an additional boost for synergies between astroparticle physics and radio astronomy will be given in the upcoming years. Specifically, this includes new short-wavelength VLBI facilities like the ngVLA and the development of advanced Southern-Hemisphere cm-band VLBI arrays in the SKA era.