SDSS DR7 superclusters. Principal component analysis

TL;DR

This study uses principal component analysis and correlation tests on SDSS DR7 superclusters to identify key properties, reveal two distinct supercluster populations, and establish fundamental scaling relations, enhancing understanding of their physical and morphological characteristics.

Contribution

The paper applies principal component analysis to supercluster data, uncovering fundamental relations and classifying superclusters into two main populations based on luminosity and shape.

Findings

Supercluster parameters do not correlate with distance.

Strong correlations exist between physical and morphological properties.

Two supercluster populations are identified based on luminosity and elongation.

Abstract

We apply the principal component analysis and Spearman's correlation test to study the properties of superclusters drawn from the SDSS DR7. We analyse possible selection effects in the supercluster catalogue, study the physical and morphological properties of superclusters, find their possible subsets, and determine scaling relations for superclusters. We show that the parameters of superclusters do not correlate with their distance. The correlations between the physical and morphological properties of superclusters are strong. Superclusters can be divided into two populations according to their total luminosity. High-luminosity superclusters form two sets, more elongated systems with the shape parameter K_1/K_2 < 0.5 and less elongated ones with K_1/K_2 > 0.5. The first two principal components account for more than 90% of the variance in the supercluster parameters and define the fundamental plane, which characterises the physical and morphological properties of superclusters. We use principal component analysis to derive scaling relations for superclusters, in which we combine the physical and morphological parameters of superclusters. Structure formation simulations for different cosmologies, and more data about the local and high redshift superclusters are needed to understand better the evolution and the properties of superclusters.