Abstract
It is widely debated whether galaxy evolution is more prone to internal or external effects. Trends to passive and/or more spheroidal populations in dense environments are widely observed and star-formation rate and stellar age and AGN fraction all correlate with measurements of the local galaxy density. However, in the hierarchical framework of galaxy formation the galaxies in the densest peaks start forming stars and assembling mass earlier making stellar mass one of the key determinants of galaxy properties. Nonetheless environmental effects are still very important and could be separated from the effect of internal galaxy properties. The Abell 901(a,b)/902 multiple cluster system at z ∼ 0.165 is a unique laboratory for galaxy evolution. Besides three main clusters it includes a few related groups. The field comprises a very broad range of galaxy environments and masses at a single redshift. Therefore by observing this single region one is able to study galaxy evolution decoupling environmental and stellar mass effects from redshift-related ones. We are currently undertaking a survey of the region with the OSIRIS tunable filter imager on the GRANTECAN. We have targeted the Hα and [NII]λ 6584 lines Together, these will provide the urgently needed star formation rate and AGN diagnostics for a full census of such properties in this field. In this talk I will present the first results of the survey on the high density regions A901a and A902 probing AGN and star formation.
