  This work presents the first results from an ESO Large Programme carried out
using the OSIRIS instrument on the 10m GTC telescope (La Palma). We have
observed a large sample of galaxies in the region of the Abell 901/902 system
(z ~ 0.165) which has been extensively studied as part of the STAGES project.
We have obtained spectrally and spatially resolved H-alpha and [NII] emission
maps for a very large sample of galaxies covering a broad range of
environments. The new data are combined with extensive multi-wavelength
observations which include HST, COMBO-17, Spitzer, Galex and XMM imaging to
study star formation and AGN activity as a function of environment and galaxy
properties such as luminosity, mass and morphology. The ultimate goal is to
understand, in detail, the effect of the environment on star formation and AGN
activity.
