Quasi-spherical superclusters

Abstract

Generally the dynamical state of superclusters is poorly known. We study properties of superclusters and select a sample of quasi-spherical superclusters, the dynamics of which can be studied using the $\Lambda$ significance diagram. We extracted our supercluster sample with an adaptive local threshold density method from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) data and estimated their masses using the dynamical masses for member galaxies and groups. We used topological analysis based on Minkowski functionals and the positions of galaxies and galaxy groups in superclusters. Finally, we highlight the dynamical state of a few exceptional types of superclusters found in this study using the $\Lambda$ significance diagram. Our final sample contains 65 superclusters in the distance range of 130 to 450 Mpc. Supercluster masses range between $1.1 \times 10^{15} M_{\sun}$ and $1.4 \times 10^{16} M_{\sun}$ and sizes between 25 Mpc and 87 Mpc. We find that pancake-type superclusters form the low-luminosity, small, poor and low-mass end of superclusters. We find four superclusters of unusual types, exhibiting exceptionally spherical shapes. These so-called quasi-spherical systems contain a high-density core surrounded by a relatively spherical density and galaxy distribution.The mass-to-light ratio of these quasi-sphericals is higher than those of the other superclusters, suggesting a relatively high dark matter content. Using the $\Lambda$ significance diagram for oblate and prolate spheroids, we find that three quasi-spherical superclusters are gravitationally bound at the present epoch. Quasi-spherical superclusters are among the largest gravitationally bound systems found to date, and form a special class of giant systems that, dynamically, are in between large gravitationally unbound superclusters and clusters of galaxies in an equilibrium configuration.

15 pages, 10 figures, 2 tables, accepted in Astronomy & Astrophysics

References in corpus (15)

• Dark Energy and the Accelerating Universe
• The Laniakea supercluster of galaxies
• Galaxy Cluster Mass Reconstruction Project: II. Quantifying scatter and bias using contrasting mock catalogues
• Galaxy Cluster Mass Reconstruction Project: I. Methods and first results on galaxy-based techniques
• A detection of the integrated Sachs-Wolfe imprint of cosmic superstructures using a matched-filter approach
• On the definition of superclusters
• The Limits of Bound Structures in the Accelerating Universe
• Sloan Great Wall as a complex of superclusters with collapsing cores
• Multiscale cosmic web detachments, connectivity, and preprocessing in the supercluster SClA2142 cocoon
• Non-Friedmann cosmology for the Local Universe, significance of the universal Hubble constant and short-distance indicators of dark energy
• Mass, Light and Colour of the Cosmic Web in the Supercluster SCL2243-0935 (z=0.447)
• Multi-scale morphology of the galaxy distribution
• Cosmic flow around local massive galaxies
• The Cosmic Large-Scale Structure in X-rays (CLASSIX) cluster survey IV: Superclusters in the local Universe at z <= 0.03
• A graph of dark energy significance on different spatial and mass scales