SIMBAD references

We analyse the properties of galaxy populations in the rich Abell cluster ABCG209 at redshift z∼0.21, on the basis of spectral classification of 102 member galaxies. We take advantage of available structural parameters to study separately the properties of bulge-dominated and disk-dominated galaxies. The star formation histories of the cluster galaxy populations are investigated by using line strengths and the 4000Å break, through a comparison to stellar population synthesis models. The dynamical properties of different spectral classes are examined in order to infer the past merging history of ABCG209. The cluster is characterized by the presence of two components: an old galaxy population, formed very early (z_f>3.5), and a younger (z_f>1.2) population of infalling galaxies. We find evidence of a merger with an infalling group of galaxies occurred 3.5-4.5Gyr ago. The correlation between the position of the young H_δ-strong galaxies and the X-ray flux shows that the hot intracluster medium triggered a starburst in this galaxy population ∼3Gyr ago.