# Using synchrotron emission modelling of relativistic hydrodynamic jet simulations to study the FR I/FR II dichotomy of Active Galactic nuclei radio jets

## TL;DR

This study uses relativistic hydrodynamic simulations combined with synchrotron emission modelling to explore the morphological differences between FR I and FR II radio galaxies, revealing how jet Lorentz factors and injection rates influence observed structures.

## Contribution

It introduces a comprehensive simulation framework that links jet dynamics with radio emission features, providing new insights into the FR I/FR II dichotomy in AGN jets.

## Key findings

- High Lorentz factor jets produce FR II-like structures with hot spots and filaments.
- Lower Lorentz factor jets can resemble FR I structures when mass injection is reduced.
- Doppler boosting effects vary with viewing angle, affecting observed morphology.

## Abstract

In this paper three dimensional relativistic hydrodynamic simulations of AGN jets are presented to investigate the FR I/FR II dichotomy. Three simulations are presented which illustrates the difference in morphology for high/low Lorentz factor injection as well as a stratified background medium. Lorentz factors of 10 and 1.0014 were used for the high and low Lorentz factor cases respectively. The hydrodynamic simulations show a division in the morphology of jets based on their initial injection luminosity. An additional simulation was set up to investigate the evolution of the low Lorentz factor jet if the mass injection was lowered after a certain time. A synchrotron emission model was applied to these simulations to reproduce intensity maps at radio frequencies (1.5GHz) which were compared to the observed emission structures of FR I/FR II radio galaxies. The effect of Doppler boosting on the intensity maps was also investigated for different polar angles. The intensity maps of both the high and low Lorentz factor cases reproduced emission structures that resemble those of FR II type radio galaxies with a dominant cocoon region containing time dependent hot spots and filaments. An FR I like structure was, however, produced for the low Lorentz factor case if the mass injection rate was lowered after a set time period.