Photometry of distant clusters of galaxies: evolutionary features in the cluster 2158 + 0351 (z = 0.45)

Results of detailed three-colour photometry of the distant cluster 2158+0351 (z=0.445) are presented. A photometric catalogue has been produced using the INVENTORY package. In total we measured Gunn g, r, i magnitudes for 294 objects, down to r=23.5, with a typical error of 0.1 mag. On the basis of a statistical analysis, about 60 per cent of these are suggested to be cluster members. Luminosity functions are shown along with colour-magnitude and two-colour diagrams. We find that the bright-cluster galaxy population is dominated by ellipticals, while a population of spirals becomes relevant at the faint luminosities. Such an overabundance of faint spirals leads us to calculate a high fraction of blue objects, according to the Butcher-Oemler effect. We evidence possible photometric effects on magnitudes and colours due to galactic evolution. (author)