# A dynamical model for FR II type radio sources with terminated jet activity

## TL;DR

This paper extends the KDA model to describe the evolution of FR II radio sources after jet activity ceases, providing improved fits to observed spectra and insights into their dynamical behavior.

## Contribution

The paper introduces the KDA EXT model, an extension of the classical KDA model, to account for jet termination in FR II sources, enhancing the understanding of their evolution.

## Key findings

- KDA EXT model better fits observed spectra than original KDA model.
- Derived formulae describe lobe length and luminosity during jet cessation.
- Application to three radio galaxies demonstrates model's effectiveness.

## Abstract

The extension of the KDA analytical model of FR II-type source evolution originally assuming a continuum injection process in the jet-IGM (intergalactic medium) interaction towards a case of the jet's termination is presented and briefly discussed. The dynamical evolution of FR II-type sources predicted with this extended model, hereafter referred to as KDA EXT, and its application to the chosen radio sources. Following the classical approach based on the source's continuous injection and self-similarity, I propose the effective formulae describing the length and luminosity evolution of the lobes during an absence of the jet flow, and present the resulting diagrams for the characteristics mentioned. Using an algorithm based on the numerical integration of a modified formula for jet power, the KDA EXT model is fitted to three radio galaxies. Their predicted spectra are then compared to the observed spectra, proving that these fits are better than the best spectral fit provided by the original KDA model of the FR II-type sources dynamical evolution.