Environment, interactions, and their effect on a sample of 300000 galaxies

The origin and evolution of galaxies is closely related to that of the central supermassive black holes (SMBH) that many of them harbour. Interactions between galaxies can trigger their central SMBHs and this nuclear activity could be the origin of the star formation quenching observed in massive galaxies located in dense environments. Hence, these feedback phenomena could play a fundamental role in galactic evolution. However, the relationship between environment and nuclear activity is not completely clear and contradictory results are found in the literature. We present a study based on a sample of ∼300000 Sloan Digital Sky Survey (SDSS) galaxies. Three environmental parameters (tidal forces, local density and cluster richness) were defined and computed for these galaxies. Nuclear activity was also classified based on optical and radio data. The discrimination between galaxy environment and one-on-one interactions and the consideration of different types of accretion (high-excitation and low-excitation) allow us to reconcile the apparently contradictory results found in the literature.