A Multiscale View of Active Galactic Nuclei Jets: from the Formation and Acceleration to High Energy Outbursts

Abstract

Active Galactic Nuclei (AGNs) often produce highly collimated relativistic jets, one of the most energetic phenomena in the Universe. In this thesis, we probe the mechanism of launching, propagation, and energy dissipation of AGN jets by using various methodologies. We study the jet of a nearby radio galaxy M87 with very long baseline interferometry observations and find that the jet is collimated by the pressure of non-relativistic winds launched from hot accretion flows and accelerated to relativistic speeds by strong magnetic fields in the jet. We investigate the frequency dependence of Faraday rotation of many AGN jets and reveal that recollimation shocks in the jets may play an important role in dissipation of the jet kinetic energy. We examine the association of strong γ-ray flares occurred in 2015 in the jet of PKS 1510–089 and its peculiar kinematic behavior and find that the flares may originate from compression of the jet knots by a standing shock in the core. We study the long-term radio variability of many radio-loud AGNs by employing temporal Fourier transform of the light curves and reveal that the radio variability can be controlled by the accretion processes. We constrain the properties of the radio-emitting source known as Sagittarius A*, which is potentially powered by jets, by a very long baseline interferometry observation during the passage of the gas cloud G2 through the vicinity of the supermassive black hole.