The large-scale environment of 3CR radio galaxies at z<0.3

Abstract

The question of whether and how the properties of radio galaxies (RGs) are connected with the large-scale environment is still an open issue. For this work we measured the large-scale galaxies' density around RGs present in the revised Third Cambridge Catalog of radio sources (3CR) with $0.02 < z < 0.3$. The goal is to determine whether the accretion mode and morphology of RGs are related to the richness of the environment. We considered RGs at $0.05 < z < 0.3$ for a comparison between optical spectroscopic classes, and those within $0.02 < z < 0.1$ to study the differences between the radio morphological types. Photometric data from the Panoramic Survey Telescope Rapid Response System (Pan-STARRS) survey were used to search for "red sequences" within an area of 500 kpc of radius around each RG. We find that 1) RGs span over a large range of local galaxies' density, from isolated sources to those in rich environments, 2) the richness distributions of the various classes are not statistically different, and 3) the radio luminosity is not connected with the source environment. Our results suggest that the RG properties are independent of the local galaxies density, which is in agreement with some previous analyses, but contrasting with other studies. We discuss the possible origin of this discrepancy. An analysis of a larger sample is needed to put out results on a stronger statistical basis.