Simulation of polarized emission from recollimation shocks in relativistic jets

Abstract

This paper presents a method for obtaining synthetic images of linearly polarized synchrotron radiation from steady-state numerical simulations of relativistic jets, in which the magnetic field is assumed to be initially either partially or completely disordered. The method is based on the earlier work which characterized the deformation of the fluid using infinitessimal fluid elements that are initially cubic, and which evolve into parallelepipeds. The method is described for a range of models for the initial magnetic field, including ordered components that are axial, helical, and toroidal with a bi-directional axial component. The method is then applied to steady, axisymmetric simulations of initially overpressured jets and the initial results are discussed. Some characteristic patterns and trends in polarization angle are identified. Although the recollimation shocks that form in these jets are not clearly visible in the total intensity images presented here, arcs of strongly polarized emission associated with radial velocity gradients in the vicinity of the shock waves are seen, and might prove to be a useful diagnostic feature of this model.