Young radio sources: the duty-cycle of the radio emission and prospects for gamma-ray emission

TL;DR

This paper explores the early stages and duty cycle of radio emission in young AGN-related radio sources, examining their potential for gamma-ray emission due to jet-environment interactions and intermittent activity.

Contribution

It investigates the prevalence and evolution of young radio sources, highlighting the role of environmental interactions and jet intermittency in their development and gamma-ray emission prospects.

Findings

Young radio sources often do not evolve into large radio galaxies.

Intermittent jet activity is common among young radio sources.

Jet-cloud interactions may facilitate gamma-ray emission detectable by Fermi-LAT.

Abstract

The evolutionary stage of a powerful radio source originated by an AGN is related to its linear size. In this context, compact symmetric objects (CSOs), which are powerful and intrinsically small objects, should represent the young stage in the individual radio source life. However, the fraction of young radio sources in flux density-limited samples is much higher than what expected from the number counts of large radio sources.This indicates that a significant fraction of young radio sources does not develop to the classical Fanaroff-Riley radio galaxies,suggesting an intermittent jet activity. As the radio jets are expanding within the dense and inhomogeneous interstellar medium,the ambient may play a role in the jet growth, for example slowing down or even disrupting its expansion when a jet-cloud interaction takes place. Moreover, this environment may provide the thermal seed photons that scattered by the lobes' electrons may be responsible for high energy emission, detectable by Fermi-LAT.