Nucleation regions in the Large-Scale Structure I. A catalogue of cores in nearby rich superclusters

TL;DR

This study identifies and catalogs dense, gravitationally bound core regions within rich superclusters using a density-based clustering algorithm, revealing that most superclusters contain at least one such core, which are key to understanding large-scale structure formation.

Contribution

The paper introduces the Density-based Core Catalogue (DCC), systematically identifying cores in superclusters and confirming their prevalence and significance in cosmic web structures.

Findings

105 cores identified in superclusters

83% of superclusters contain at least one core

Cores are the densest, most massive features in the cosmic web

Abstract

We applied a Density-Based Clustering algorithm on samples of galaxies and galaxy systems belonging to 53 rich superclusters from the \textit{Main SuperCluster Catalogue} (MSCC) to identify the presence of ``central regions'', or \emph{cores}, in these large-scale structures. \emph{Cores} are defined here as large gravitationally bound galaxy structures, comprised of two or more clusters and groups, with sufficient matter density to survive cosmic expansion and virialize in the future. We identified a total of 105 galaxy structures classified as \emph{cores}, which exhibit a high density contrast of mass and galaxies. The Density-based \textit{Core} Catalogue (DCC), presented here, includes \emph{cores} that were previously reported in well-known superclusters of the Local Universe, and also several newly identified ones. We found that 83\% of the rich superclusters in our sample have at least one \emph{core}. While more than three \emph{cores} with different dynamical state are possible, the presence of a single \emph{core} in the superclusters is more common. Our work confirms the existence of nucleation regions in the internal structure of most rich superclusters and points to the fact that these \emph{cores} are the densest and most massive features that can be identified in the cosmic web with high probability for future virialization.