Unusual A2142 supercluster with a collapsing core: distribution of light and mass

Context. Superclusters of galaxies can be used to test cosmological models of the formation and evolution of the largest structur es in the cosmic web, and of galaxy and cluster evolution in superclusters. Aims. We study the distribution, masses, and dynamical properties of galaxy groups in the A2142 supercluster. Methods. We analyse the global luminosity density distribution in the supercluster and divide the supercluster into the high-de nsity core and the low-density outskirts regions. We find galaxy gr oups and filaments in these regions, calculate their masses a nd mass-tolight ratios and analyse their dynamical state with 1D and 3D statistics. We use the spherical collapse model to study the dynamical state of the supercluster. Results. In the A2142 supercluster rich groups and clusters lie along an almost straight line forming the 50 h −1 Mpc long main body of the supercluster. The A2142 supercluster has a very high density core surrounded by lower-density outskirts. The total estimated mass of the supercluster is Mest = 6.2× 10 15 M⊙. More than a half of groups with at least ten member galaxies in the supercluster lie in the high-density core of the supercluster, centred at the X-ray cluster A2142. Most of the groups in the core region are multimodal. In the outskirts of the supercluster, the number of groups is larger than in the core, and groups are poorer. The orientati on of the axis of the cluster A2142 follows the orientations of its X-ray substructures and radio halo, and is aligned along the supercl uster axis. The high-density core of the supercluster with the global densi ty D8≥ 17 and perhaps with D8≥ 13 may have started to collapse. Conclusions. A2142 supercluster with collapsing core and straight body, is an unusual object among superclusters. In the course of the future evolution, the supercluster may split into sever al systems.