2017MNRAS.472..409L

We investigated the variation in the fraction of optical active galactic nuclei (AGNs) hosts with stellar mass, as well as their local and global environments. Our sample is composed of cluster members and field galaxies at z <= 0.1 and we consider only strong AGN. We find a strong variation in the AGN fraction (F_AGN) with stellar mass. The field population comprises a higher AGN fraction compared to the global cluster population, especially for objects with log M_* > 10.6. Hence, we restricted our analysis to more massive objects. We detected a smooth variation in the F_AGN with local stellar mass density for cluster objects, reaching a plateau in the field environment. As a function of cluster-centric distance we verify that F_AGN is roughly constant for R > R₂₀₀, but show a steep decline inwards. We have also verified the dependence of the AGN population on cluster velocity dispersion, finding a constant behaviour for low mass systems (σ_P <= 650-700 km s^–1). However, there is a strong decline in F_AGN for higher mass clusters (>700 km s^–1). When comparing the F_AGN in clusters with or without substructure, we only find different results for objects at large radii (R > R₂₀₀), in the sense that clusters with substructure present some excess in the AGN fraction. Finally, we have found that the phase-space distribution of AGN cluster members is significantly different than other populations. Due to the environmental dependence of F_AGN and their phase-space distribution, we interpret AGN to be the result of galaxy interactions, favoured in environments where the relative velocities are low, typical of the field, low mass groups or cluster outskirts.