Modelling Optical Emission and Polarization of Relativistic AGN Jets Using RMHD Simulations

Abstract

Radio-loud Active Galactic Nuclei (AGN) exhibit non-thermal emission observed to span the entire electromagnetic spectrum. The majority of the emission at lower energies (from radio to soft X-rays) is produced by synchrotron emission of non-thermal electrons within a relativistic jet. The structure and kinematics of these relativistic jets can be simulated using relativistic magneto-hydrodynamic (RMHD) simulations. A 3D RMHD simulation was set up with the PLUTO code that consisted of a uniform background medium with a less dense jet. A domain size of 5 pc was used to model the sub-parsec region. The jet was separated into two regions, namely the spine (the inner region of the jet) and the sheath (the outer region of the jet). The spine had a radius of 0.033 pc and a maximum bulk Lorentz factor of Γmax = 10, while the sheath had a radius of 0.1 pc and a maximum bulk Lorentz factor of Γmax = 3. A helical magnetic field orientation was utilized where the spine and sheath had a maximum magnetic field magnitude of B = 50 mG and B = 5 mG, respectively. Lagrangian particles were injected at the base of the jet with an initial power-law distribution, and were allowed to evolve with time. The synchrotron and linear polarization emission coefficients were then integrated along a user defined line of sight to produce the I, Q and U Stokes parameters. We present the initial results from this study showing the spectral energy distribution (SED) and wavelength dependent polarization. © Copyright owned by the author(s) under the terms of the Creative Commons.