Superclusters of galaxies in the 2dF redshift survey. III. The properties of galaxies in superclusters

TL;DR

This study analyzes galaxy properties within superclusters from the 2dF survey, revealing that supercluster richness and density influence galaxy types, luminosities, and star formation activity, highlighting the impact of local and global environments.

Contribution

It provides a comparative analysis of galaxy properties across different supercluster densities and environments, emphasizing the influence of supercluster richness on galaxy evolution.

Findings

Rich superclusters have higher median luminosity densities than poor ones.

High density cores in rich superclusters contain more early type, passive galaxies.

Galaxies in rich superclusters tend to be more luminous than those in poor superclusters or the field.

Abstract

We use catalogues of superclusters of galaxies from the 2dF Galaxy Redshift Survey to study the properties of galaxies in superclusters. We compare the properties of galaxies in high and low density regions of rich superclusters, in poor superclusters and in the field, as well as in groups, and of isolated galaxies in superclusters of various richness. We show that in rich superclusters the values of the luminosity density smoothed on a scale of 8 \Mpc are higher than in poor superclusters: the median density in rich superclusters is $\delta \approx 7.5$, in poor superclusters $\delta \approx 6.0$. Rich superclusters contain high density cores with densities $\delta > 10$ while in poor superclusters such high density cores are absent. The properties of galaxies in rich and poor superclusters and in the field are different: the fraction of early type, passive galaxies in rich superclusters is slightly larger than in poor superclusters, and is the smallest among the field galaxies. Most importantly, in high density cores of rich superclusters ($\delta > 10$) there is an excess of early type, passive galaxies in groups and clusters, as well as among those which do not belong to groups or clusters. The main galaxies of superclusters have a rather limited range of absolute magnitudes. The main galaxies of rich superclusters have larger luminosities than those of poor superclusters and of groups in the field. Our results show that both the local (group/cluster) environments and global (supercluster) environments influence galaxy morphologies and their star formation activity.