The environmental properties of radio-emitting AGN

We study the environmental properties of z less than or similar to 1.2 radio-selected active galactic nuclei (AGNs) belonging to the similar to 2 deg(2) of the COSMOS field, finding that about 20 per cent of them appear within overdense structures. AGNs with P-1.4 GHz > 10(23.5) W Hz(-1) sr(-1) are twice more likely to be found in clusters with respect to fainter sources (similar to 38 per cent vs similar to 15 per cent), just as radio-selected AGNs with stellar masses M-* > 10(11) M-circle dot are twice more likely to be found in overdense environments with respect to objects of lower mass (similar to 24 per cent vs similar to 11 per cent). Comparisons with galaxy samples further suggest that radio-selected AGN of large stellar mass tend to avoid underdense environments more than normal galaxies with the same stellar content. Stellar masses also seem to determine the location of radio-active AGN within clusters: similar to 100 per cent of the sources found as satellite galaxies have M* < 10(11.3) M-circle dot, while similar to 100 per cent of the AGNs coinciding with a cluster central galaxy have M* > 10(11) M-circle dot. No different location within the cluster is instead observed for AGN of various radio luminosities. Radio AGN, which also emit in the Mid-Infrared show a marked preference to be found as isolated galaxies (similar to 70 per cent) at variance with those also active in the X-ray that all seem to reside within overdensities. What emerges from our work is a scenario whereby physical processes on sub-pc and kpc scales (e.g. emission, respectively, related to the AGN and to star formation) are strongly interconnected with the large-scale environment of the AGN itself.