Superclusters of galaxies in the 2dF redshift survey -: III.: The properties of galaxies in superclusters

Context. Superclusters are the largest systems in the Universe to give us information about the very early Universe. Our present series of papers is devoted to the study of the properties of superclusters of galaxies from the 2dF Galaxy Redshift survey. Aims. We use catalogues of superclusters of galaxies from the 2dF Galaxy Redshift Survey to compare the properties of rich and poor superclusters. In particular, we study the properties of galaxies ( spectral types, colours, and luminosities) in superclusters. Methods. We compare the distribution of densities in rich and poor superclusters, and the properties of galaxies in high and low-density regions of rich superclusters, in poor superclusters, and in the field. In superclusters and in the field, we also compare the properties of galaxies in groups, and the properties of those galaxies which do not belong to any group. Results. We show that in rich superclusters the values of the luminosity density smoothed on a scale of 8 h(-1) Mpc are higher than in poor superclusters: the median density in rich superclusters is delta approximate to 7.5 and in poor superclusters delta approximate to 6.0. Rich superclusters contain high-density cores with densities delta > 10, while in poor superclusters such high-density cores are absent. The properties of galaxies in rich and poor superclusters and in the field are different: the fraction of early type, passive galaxies in rich superclusters is slightly higher than in poor superclusters, and is the lowest among the field galaxies. Most importantly, in high-density cores of rich superclusters ( d > 10), there is an excess of early type, passive galaxies in groups and clusters, as well as among those which do not belong to any group. The main galaxies of superclusters have a rather limited range of absolute magnitudes. The main galaxies of rich superclusters have higher luminosities than those of poor superclusters and of groups in the field. Conclusions. Our results show that both the local (group/cluster) environments and global (supercluster) environments influence galaxy morphologies and their star formation activity.