The role of environment in the observed Fundamental Plane of radio active galactic nuclei

The optical Fundamental Plane of black hole activity relates radio continuum luminosity of active galactic nuclei (AGNs) to [OⅠⅠⅠ] luminosity and black hole mass. We examine the environments of low-redshift (𝓏 < 0.2) radio-selected AGNs, quantified through galaxy clustering, and find that halo mass provides similar mass scalings to black hole mass in the Fundamental Plane relations. AGN properties are strongly environment-dependent: massive haloes are more likely to host radiatively inefficient (low-excitation) radio AGN, as well as a higher fraction of radio luminous, extended sources. These AGN populations have different radio-optical luminosity scaling relations, and the observed mass scalings in the parent AGN sample are built up by combining populations preferentially residing in different environments. Accounting for environment-driven selection effects, the optical Fundamental Plane of supermassive black holes is likely to be mass-independent, as predicted by models.