2003A&A...408...57M

We derive the luminosity functions in three bands (BVR) for the rich galaxy cluster ABCG209 at z=0.21. The data cover an area of ∼78arcmin² in the B and R bands, while a mosaic of three pointings was obtained in the V band, covering an area of approximately 160arcmin². The galaxy sample is complete to B=22.8 (N_gal=339), V=22.5 (N_gal=1078) and R=22.0 (N_gal=679). Although the fit of a single Schechter function cannot be rejected in any band, the luminosity functions are better described by a sum of two Schechter functions for bright and faint galaxies, respectively. There is an indication for a presence of a dip in the luminosity functions in the range V=20.5-21.5 and R=20.0-21.0. We find a marked luminosity segregation, in the sense that the number ratio of bright-to-faint galaxies decreases by a factor 4 from the center to outer regions. Our analysis supports the idea that ABCG209 is an evolved cluster, resulting from the merger of two or more sub-clusters.