The richest superclusters I. Morphology

Context. Superclusters are the largest systems in the Universe to give us information about the formation and evolution of structures in the very early Universe. Our present series of papers is devoted to the study of the morphology and internal structure of superclusters of galaxies. Aims. We study the morphology of the richest superclusters from the catalogs of superclusters of galaxies in the 2dF Galaxy Redshift Survey and compare the morphology of real superclusters with model superclusters in the Millennium Simulation. Methods. We use Minkowski functionals and shapenders to quantify the morphology of superclusters: their sizes, shapes, and clumpiness. We generate empirical models of simple geometry to understand which morphologies correspond to the supercluster shapenders (Appendix A). Results. Rich superclusters have elongated, lamentary shapes with high-density clumps in their core regions. The clumpiness of superclusters is determined using the fourth Minkowski functional V3. In the K1-K2 shapender plane the morphology of superclusters is described by a curve which is characteristic of multi-branching laments as shown by our empirical models. We found several dierences between observed and model superclusters. The curves of the fourth Minkowski functional V3 for ob-served and model superclusters have dierent shapes indicating that their structure is dierent. The values of V3 for the supercluster SCL126 (the Sloan Great Wall) show that this supercluster has a very high density core which is absent in other superclusters. Th