To obtain a physically well-motivated definition of superclusters, we proposed in our previous work to select superclusters with an overdensity criterion that selects only those objects that will collapse in the future, including those that are at a turn-around in the present epoch. In this paper we present numerical values for these criteria for a range of standard cosmological models. We express these criteria in terms of a density ratio or, alternatively, as an infall velocity and show that these two criteria give almost identical results. To better illustrate the implications of this definition, we applied our criteria to some prominent structures in the local Universe, the Local supercluster, Shapley supercluster, and the recently reported Laniakea supercluster to understand their future evolution. We find that for the Local and Shapley superclusters, only the central regions will collapse in the future, while Laniakea does not constitute a significant overdensity and will disperse in the future. Finally, we suggest that those superclusters that will survive the accelerating cosmic expansion and collapse in the future be called "superstes-clusters", where "superstes" means survivor in Latin, to distinguish them from traditional superclusters.
|Journal||Astronomy and Astrophysics|
|State||Published - Mar 2015|
Bibliographical noteFunding Information:
We thank the referee for the useful comments. H.B. acknowledges support from the DfG Transregio Programme TR33 and the DFG cluster of excellence “Origin and Structure of the Universe” ( www.universe-cluster.de ). G.C. acknowledges the support from the Deutsches Zentrum für Luft- und Raumfahrt (DLR) with the programme 50 OR 1403. S.Z. would like to acknowledge the support of The Netherlands Organisation for Scientific Research (NWO) VICI grant and Munich Institute for Astro- and Particle Physics (MIAPP) of the DFG cluster of excellence.
© ESO, 2015.
- X-rays: galaxies: clusters
- large-scale structure of Universe