New prediction of extragalactic GeV gamma-ray emission from radio lobes of young AGN jets

TL;DR

This paper predicts GeV gamma-ray emission from young AGN radio lobes by including cooling effects, suggesting nearby lobes could be detectable with Fermi, advancing understanding of AGN jet evolution.

Contribution

It introduces a new model incorporating cooling effects into gamma-ray emission predictions from young AGN radio lobes, improving upon previous no-cooling models.

Findings

Lobes start with electron temperatures around GeV and cool to MeV.

Predicted GeV gamma-ray luminosity diminishes over time due to cooling.

Nearby young radio lobes may be detectable by Fermi.

Abstract

We present a new prediction of GeV $\gamma$-ray emission from radio lobes of young AGN jets. In the previous work of Kino et al. (2007), MeV $\gamma$-ray bremsstrahlung emission was predicted from young cocoons/radio-lobes in the regime of no coolings. In this study, we include cooling effects of bremsstrahlung emission and adiabatic loss. With the initial conditions determined by observed young radio lobes, we solve a set of equations describing the expanding lobe evolution. Then we find that the lobes initially have electron temperature of $\sim$GeV, and they cool down to $\sim$MeV by the adiabatic loss. Correspondingly, the lobes initially yield bright bremsstrahlung luminosity in $\sim$GeV range and they fade out. We estimate these $\gamma$-ray emissions and show that nearby young radio lobes could be detected with Fermi Gamma-ray Space Telescope.