  The thesis work is focused on the analysis of the galaxy clusters ABCG 209,
at z~0.2, which is characterized by a strong dynamical evolution. The data
sample used is based mainly on new optical data (EMMI-NTT: B, V and R band
images and MOS spectra), acquired in October 2001 at the European Southern
Observatory in Chile. Archive optical data (CFHR12k: B and R images), and X-ray
(Chandra) and radio (VLA) observations are also analysed. The main goal of the
present analysis is the investigation of the connection between internal
cluster dynamics and star formation history, aimed at understanding the complex
mechanisms of cluster formation and evolution. The analysis of the internal
dynamics of the cluster and the study of the galaxy luminosity function (LF)
suggest an observational scenario in which ABCG 209 is undergoing a strong
dynamical evolution with the merging of two or more subclumps along the SE-NW
direction in a plane which is not parallel to the plane of sky. The effect of
cluster environment on the global properties of the cluster galaxies is
examined through the analysis of the LFs, colour-magnitude relations, and
average colours.Moreover cluster dynamics and large-scale structure have a
strong influence on galaxy evolution, so it is performed a detailed study of
spectroscopic properties of 102 luminous member galaxies. All the results
support an evolutionary scenario in which ABCG 209 is characterized by a sum of
two components: an old galaxy population, formed very earlier (z >~ 3), and a
younger population of infalling galaxies. Moreover this cluster may have
experimented 1 or 2 Gyrs ago a merging with an infalling galaxy group, as
indicated also by the previous dynamical analysis.
