Morphological Properties of Superclusters of Galaxies

TL;DR

This study analyzes the shapes and properties of superclusters of galaxies using SDSS data and simulations, revealing that filamentary superclusters are generally richer, larger, and more luminous than pancake-shaped ones.

Contribution

It introduces a morphological analysis of superclusters using Minkowski Functionals and compares observed data with mock catalogues to assess biases and robustness.

Findings

Filamentary superclusters are richer and more luminous.

Supercluster morphology correlates with size and luminosity.

Results are consistent across observed and simulated data.

Abstract

We studied superclusters of galaxies in a volume-limited sample extracted from the Sloan Digital Sky Survey Data Release 7 (SDSS/DR7) and from mock catalogues based on a semi-analytical model of galaxy evolution in the Millenium Simulation. A density field method was applied to a sample of galaxies brighter than $M_r= -21+5 \log h_{100}$ to identify superclusters, taking into account selection and boundary effects. In order to evaluate the influence of threshold density, we have chosen two thresholds: the first maximizes the number of objects (D1), and the second constrains the maximum supercluster size to $\sim$120~h$^{-1}$Mpc (D2). We have performed a morphological analysis, using Minkowski Functionals, based on a parameter which increases monotonically from filaments to pancakes. An anti-correlation was found between supercluster richness (and total luminosity or size) and the morphological parameter, indicating that filamentary structures tend to be richer, larger and more luminous than pancakes in both observed and mock catalogues. We have also used the mock samples to compare supercluster morphologies identified in position and velocity spaces, concluding that our morphological classification is not biased by the peculiar velocities. Monte Carlo simulations designed to investigate the reliability of our results with respect to random fluctuations show that these results are robust. Our analysis indicates that filaments and pancakes present different luminosity and size distributions.