Radio galaxies in galaxy groups: kinematics, scaling relations and AGN feedback

Abstract

We investigate the kinematic properties of a large (N=998) sample of COSMOS spectroscopic galaxy members distributed among 79 groups. We identify the Brightest Group Galaxies (BGGs) and cross-match our data with the VLA-COSMOS Deep survey at 1.4 GHz, classifying our parent sample into radio/non-radio BGGs and radio/nonradio satellites. The radio luminosity distribution spans from L R ∼ 2 × 10 21 W Hz −1 to L R ∼ 3×10 25 W Hz −1 . A phase-space analysis, performed by comparing the velocity ratio (line-of-sight velocity divided by the group velocity dispersion) with the galaxy-group centre offset, reveals that BGGs (radio and non-radio) are mostly (∼80%) ancient infallers. Furthermore, the strongest (L R > 10 23 W Hz −1 ) radio galaxies are always found within 0.2R vir from the group centre. Comparing our samples with HORIZON-AGN, we find that the velocities and offsets of simulated galaxies are more similar to radio BGGs than to non-radio BGGs, albeit statistical tests still highlight significant differences between simulated and real objects. We find that radio BGGs are more likely to be hosted in high-mass groups. Finally, we observe correlations between the powers of BGG radio galaxies and the X-ray temperatures, T x , and X-ray luminosities, L x , of the host groups. This supports the existence of a link between the intragroup medium and the central radio source. The occurrence of powerful radio galaxies at group centres can be explained by Chaotic Cold Accretion, as the AGN can feed from both the galactic and intragroup condensation, leading to the observed positive L R − T x correlation.

The eROSITA Final Equatorial-Depth Survey (eFEDS): LOFAR view of brightest cluster galaxies and AGN feedback

“…Large offsets (100-1000 kpc) are often an indication of a strongly disturbed cluster environment (Rossetti et al 2016;De Propris et al 2021, and references therein). The relation between BCGs, the triggering of the AGN and the offset from the cluster centre has been widely discussed and was recently studied in Pasini et al (2021a). In that paper, the authors found that it is more common for more central BCGs to show radio-loud AGN since in these galaxies the accretion onto the central BH is boosted by the strong cooling in the cluster core.…”

“…They also discuss a correlation between the X-ray luminosity of groups and the radio power from the central radio galaxy since more massive groups seem to host more powerful sources. Indeed, Pasini et al (2021a) recently showed that, in their sample of groups, BGGs showing powerful radio emission are always found within 0.2 R vir ∼ 0.3R 200 from the centre.…”

The environments of the radio galaxy population in SIMBA

“…Using x-ray observations with the Chandra and XMM-Newton, Ineson et al (2015) shows that there are strong correlations between the radio luminosity and cluster luminosity for LERGs, though not for HERGs; however, these results are restricted to the most luminous clusters. It is expected that the luminosity of the central radio galaxy scales with the X-ray luminosity of the cluster (Pasini et al 2020(Pasini et al , 2021, implying that brighter radio galaxies populate richer environments (Best 2004;Ching et al 2017;Croston et al 2018).…”