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