Radio source evolution

TL;DR

This paper reviews the theoretical and numerical understanding of radio source evolution using the $P-D$ diagram, highlighting how jet power and environment influence their evolutionary tracks.

Contribution

It provides a synthesis of current models and simulations explaining radio source evolution, emphasizing the role of host galaxy and intergalactic medium effects.

Findings

Low-power jets are decelerated within host galaxies, explaining the excess of compact sources.

Numerical simulations support the deceleration hypothesis for small-sized radio sources.

Different evolutionary tracks are proposed based on physical processes affecting radio sources.

Abstract

Baldwin (1982) wrote that \emph{the distribution of sources in the radio luminosity, $P$, overall physical size, $D$, diagram} could be considered as \emph{the radio astronomer's $H-R$ diagram}. However, unlike the case of stars, not only the intrinsic properties of the jets, but also those of the host galaxy and the intergalactic medium are relevant to explain the evolutionary tracks of radio radio sources. In this contribution I review the current status of our understanding of the evolution of radio sources from a theoretical and numerical perspective, using the $P-D$ diagram as a framework. An excess of compact (linear size $\leq 10$~kpc) sources could be explained by low-power jets being decelerated within the host galaxy, as shown by recent numerical simulations. Finally, I discuss the possible tracks that radio sources may follow within this diagram, and the physical processes that can explain the different tracks.