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

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.

The relation between the radio emission of the core and host galaxy properties in Fanaroff-Riley type II radio galaxies

“…11). The core FRIIs are on average larger compared to the non-core FRIIs consistent with the result presented in Bruni et al [2018]. Although we could not distinguish between the radio emissions from small scale jets with those of new born jets, we could slightly modify our results for the observed differences in the physical radio sizes by comparing core and non-core samples with the same distributions of radio sizes.…”

“…They are also the largest radio galaxies in size. Bruni et al [2018] showed 80 percent of a sample of giant radio galaxies show signs of restarting radio AGN activity consistent with this picture. In addition, Mingo et al [2019] presented a new emerging type of radio galaxies called core-D which are core-dominated FRIs with the bright ends like FRIIs.…”