# Probing restarting activity in hard X-ray selected giant radio galaxies

## TL;DR

This study investigates the restarting activity in giant radio galaxies, revealing that a significant portion shows signs of multiple jet activity episodes, supported by X-ray and radio observations.

## Contribution

It provides evidence that many giant radio galaxies have undergone multiple activity episodes, highlighting the role of restarting activity in their large sizes.

## Key findings

- 22% of sources are giant radio galaxies, higher than typical radio catalogues.
- 80% of the sample shows signs of restarting radio activity.
- X-ray properties indicate high-accretion states during restarting phases.

## Abstract

With their sizes larger than 0.7 Mpc, Giant Radio Galaxies (GRGs) are the largest individual objects in the Universe. To date, the reason why they reach such enormous extensions is still unclear. One of the proposed scenarios suggests that they are the result of multiple episodes of jet activity. Cross-correlating the INTEGRAL+Swift AGN population with radio catalogues (NVSS, FIRST, SUMSS), we found that 22% of the sources are GRG (a factor four higher than those selected from radio catalogues). Remarkably, 80% of the sample shows signs of restarting radio activity. The X-ray properties are consistent with this scenario, the sources being in a high-accretion, high-luminosity state with respect to the previous activity responsible for the radio lobes.