Shapley supercluster survey: mapping the dark matter distribution

Abstract

ABSTRACT We present a 23 deg2 weak gravitational lensing survey of the Shapley supercluster core and its surroundings using gri VST images as part of the Shapley Supercluster Survey (ShaSS). This study reveals the overall matter distribution over a region containing 11 clusters at z ∼ 0.048 that are all interconnected, as well as several ongoing cluster–cluster interactions. Galaxy shapes have been measured by using the Kaiser–Squires–Broadhurst method for the g- and r-band images and background galaxies were selected via the gri colour–colour diagram. This technique has allowed us to detect all of the clusters, either in the g- or r-band images, although at different σ levels, indicating that the underlying dark matter distribution is tightly correlated with the number density of the member galaxies. The deeper r-band images have traced the five interacting clusters in the supercluster core as a single coherent structure, confirmed the presence of a filament extending North from the core, and have revealed a background cluster at z ∼ 0.17. We have measured the masses of the four richest clusters (A3556, A3558, A3560, and A3562) in the two-dimensional shear pattern, assuming a spherical Navarro–Frenk–White profile and obtaining a total mass of $\mathcal {M}_{\rm ShaSS,WL}{=}1.56^{+0.81}_{-0.55}{\times }10^{15\, }{\rm M}_{\odot }$, which is consistent with dynamical and X-ray studies. Our analysis provides further evidence of the ongoing dynamical evolution in the ShaSS region.