CODEX: Role of velocity substructure in the scaling relations of galaxy clusters

TL;DR

This study investigates how velocity substructure and X-ray-to-optical offsets influence the scaling relations of galaxy clusters, revealing that substructure increases scatter and that these effects vary with redshift, impacting cluster-based cosmology.

Contribution

It provides a detailed analysis of the impact of velocity substructure and X-ray offsets on cluster scaling relations using spectroscopic data, updating the CODEX cluster catalog.

Findings

Clusters with velocity substructure show higher velocity dispersion and increased scatter.

X-ray-to-optical offsets produce similar effects on scaling relations as substructure.

Scatter in scaling relations decreases with redshift, especially below z<0.15.

Abstract

The use of galaxy clusters as cosmological probes relies on a detailed understanding of their properties. We aim to update the spectroscopic cluster identification of CODEX by running the spectroscopic group finder on the follow-up spectroscopy results and connecting the dynamical state of clusters to their scaling relations. We implemented a reproducible spectroscopic membership determination and cleaning procedures, based on the redMaPPer membership, running the spectroscopic group finder on the follow-up spectroscopy results and cleaning the membership for spectroscopic outliers. We applied the Anderson-Darling test for velocity substructure and analysed its influence on the scaling relations. We also tested the effect of the X-ray-to-optical centre offset on the scaling relations. We report on the scaling relations between richness, X-ray luminosity, and velocity dispersion for a complete sample of clusters with at least 15 members. Clusters with velocity substructure exhibit enhanced velocity dispersion for a given richness and are characterized by 2.5 times larger scatter. Clusters that have a strong offset in X-ray-to-optical centres have comparable scaling relations as clusters with substructure. We demonstrate that there is a consistency in the parameters of the scaling relations for the low- and high-richness galaxy clusters. Splitting the clusters by redshift, we note a decrease in scatter with redshift in all scaling relations. We localize the redshift range where a high scatter is observed to $z<0.15$, which is in agreement with the literature results on the scatter. We note that the increase in scatter for both high- and low-luminosity clusters is $z<0.15$, suggesting that both cooling and the resulting active galactic nucleus feedback are at the root of this scatter. Abridged.