AGN on the Beach

Jet formation and physics

Studying the link between radio galaxies and AGN fuelling with relativistic hydrodynamic simulations of flickering jets

James Matthews

 Mo, 15:00 ! Livein  Palazzo Santa Chiarafor  15min

Flickering variability is ubiquitous in accreting sources and occurs within the chaotic cold accretion model. In addition, jetted AGN show evidence of variability in their morphologies. Despite this, many theoretical studies focus on steady or “on-off” jets. I will present new work in which we characterise AGN jet variability as a noisy process, and conduct kpc-scale hydrodynamic simulations in which the jet power varies with flicker noise properties. We find the dynamics of the jet cocoon depend on the variability amplitude with a clear link between the cocoon shape and historical activity. The jet advances quickly during high states, whereas low states resemble Sedov blast waves. Periods of high activity create stronger backflow, and the variability leads to propagating internal shocks. In addition, we use synthetic images to show that jet variability creates dramatic changes in hotspot structure, lobe morphology and brightness distributions. We discuss various implications, including for observations and particle acceleration, and estimate the scatter introduced to power-luminosity correlations. Overall, we propose that radio galaxies are an important diagnostic of Myr timescale AGN fuelling, due to their `long-term memory’.

 Overview  Program