Modeling the Emission from Turbulent Relativistic Jets in Active Galactic Nuclei

TL;DR

This paper develops a numerical model to simulate the flux variability of turbulent relativistic jets in active galactic nuclei, accounting for Doppler boosting, turbulence spectra, and time delays, to match observed AGN variability.

Contribution

It introduces a comprehensive numerical framework incorporating relativistic turbulence spectra and time delay effects to model AGN jet emission variability.

Findings

PSD slopes depend on turbulent velocity

Flux variations match observed AGN variability

Model accommodates different turbulence spectra

Abstract

We present a numerical model developed to calculate observed fluxes of relativistic jets in active galactic nuclei. The observed flux of each turbulent eddy is dependent upon its variable Doppler boosting factor, computed as a function of the relativistic sum of the individual eddy and bulk jet velocities and our viewing angle to the jet. The total observed flux is found by integrating the radiation from the eddies over the turbulent spectrum. We consider jets that contain turbulent eddies that have either standard Kolmogorov or recently derived relativistic turbulence spectra. We also account for the time delays in receiving the emission of the eddies due to their different simulated positions in the jet, as well as due to the varying beaming directions as they turn over. We examine these theoretical light curves and compute power spectral densities (PSDs) for a range of viewing angles, bulk velocities of the jet, and turbulent velocities. These PSD slopes depend significantly on the turbulent velocity and are essentially independent of viewing angle and bulk velocity. The flux variations produced in the simulations for realistic values of the parameters tested are consistent with the types of variations observed in radio-loud AGN as, for example, recently measured with the Kepler satellite, as long as the turbulent velocities are not too high.