Description
Simulations provide a way to connect observations from large-scale surveys of AGN jets to the evolution of these systems. This evolution is closely connected to the accretion process and fuelling physics, which is often variable on a range of timescales. We study this connection by conducting relativistic hydrodynamics (RHD) simulations using the PLUTO code. We use the Lagrangian particle module (Vaidya, B. et al. 2018) to track the energy spectra of non-thermal electrons, allowing us to more accurately predict synchrotron spectra and study the mixing of particle populations. We use these simulations to assess the applicability of spectral ageing models to radio observations and to search for markers of long-term flickering variability in accretion rate, as expected from chaotic accretion.
Estimating the ages of AGN is key to understanding the duty cycle and jet power of these systems. Our results suggest that periods of high jet power can lead to increased injection of energy into newly shocked material. This can reduce the apparent age of a source and lead to distinct patches of recently shocked material far back into the lobes. We find cases where relatively small changes in jet power mimic a restarting jet. We study the formation of knots along the jet due to recollimation shocks, with implications for high energy observations.
Overall, our results highlight the overall importance of jet variability for understanding the AGN jet population and show that synchrotron electrons could act as a unique probe of Myr timescale flickering in AGN.
