The matter distribution in z ~ 0.5 redshift clusters of galaxies. II : The link between dark and visible matter

TL;DR

This study analyzes the distribution of dark and visible matter in 11 galaxy clusters at z ~ 0.5 using weak lensing and optical data, confirming strong correlations but noting some discrepancies in merging clusters.

Contribution

It provides detailed mass maps from weak lensing and compares dark matter with galaxy light distribution in intermediate-redshift clusters, including new optical analyses of some clusters.

Findings

Dark matter and galaxy distributions are strongly correlated.

Average M/L ratio is 160 +/- 60 in solar units.

Some discrepancies observed in merging or perturbed clusters.

Abstract

We present an optical analysis of a sample of 11 clusters built from the EXCPRES sample of X-ray selected clusters at intermediate redshift (z ~ 0.5). With a careful selection of the background galaxies we provide the mass maps reconstructed from the weak lensing by the clusters. We compare them with the light distribution traced by the early-type galaxies selected along the red sequence for each cluster. The strong correlations between dark matter and galaxy distributions are confirmed, although some discrepancies arise, mostly for merging or perturbed clusters. The average M/L ratio of the clusters is found to be: M/L_r = 160 +/- 60 in solar units (with no evolutionary correction), in excellent agreement with similar previous studies. No strong evolutionary effects are identified even if the small sample size reduces the significance of the result. We also provide a individual analysis of each cluster in the sample with a comparison between the dark matter, the galaxies and the gas distributions. Some of the clusters are studied for the first time in the optical.