Locating the Dominant Site of Energy Dissipation in Powerful Extragalactic Jets and Understanding Large Scale Jet Dynamics

Accretion onto the supermassive black hole in some active galactic nuclei (AGN) drives relativistic jets of plasma, which can remain stable beyond their host galaxy, reaching up to megaparsec scales. In this dissertation, I study AGN jets at two vastly different scales. Powerful jets dissipate a large fraction of their kinetic energy into gamma-rays at roughly parsec-scales. Previous studies have been unable to constrain the location between possibilities ranging from the sub-parsec-scale broad-line region to the parsec-scale molecular torus, and beyond. I have utilized a simple diagnostic, based solely on observable properties, to determine that the more distant molecular torus is the dominant location of energy dissipation in powerful jets (Harvey, ALW et al., accepted, Nature Communications). At the opposite end of the length-scale, kiloparsec-scale jets reach the boundary between the host interstellar medium and the external intergalactic medium, and can be strongly disrupted by material external to the jet. The nearby jet of M87 displays an apparent helical pattern interspersed by knots of strong emission. Using Hubble Space Telescope imaging, I measure the proper motions of this jet, and constrain the mechanisms behind this behavior.