The distribution of dark matter and gas spanning six megaparsecs around the post-merger galaxy cluster MS0451-03

TL;DR

This study maps the dark matter and gas distribution around galaxy cluster MS0451-03 over six megaparsecs, revealing filamentary structures and contrasting dark matter and gas configurations consistent with a post-merger scenario.

Contribution

It provides the first detailed large-scale dark matter map around this cluster, combining lensing and X-ray data to analyze its post-merger state and filamentary environment.

Findings

Dark matter distribution is elongated and contains filaments.

Gas distribution is more spherical with lower concentration.

Cluster shows signs of a major merger 2-7 Gyr ago.

Abstract

Using the largest mosaic of Hubble Space Telescope images around a galaxy cluster, we map the distribution of dark matter throughout a $\sim$$6\times6$ Mpc$^2$ area centred on the cluster MS 0451-03 ($z=0.54$, $M_{200}=1.65\times10^{15} \rm{M}_\odot$). Our joint strong- and weak-lensing analysis shows three possible filaments extending from the cluster, encompassing six group-scale substructures. The dark-matter distribution in the cluster core is elongated, consists of two distinct components, and is characterized by a concentration parameter of $c_{200}=3.79\pm0.36$. By contrast, XMM-Newton observations show the gas distribution to be more spherical, with excess entropy near the core, and a lower concentration of $c_{200}=2.35^{+0.89}_{-0.70}$ (assuming hydrostatic equilibrium). Such a configuration is predicted in simulations of major mergers 2-7Gyr after the first core passage, when the two dark-matter halos approach second turnaround, and before their gas has relaxed. This post-merger scenario finds further support in optical spectroscopy of the cluster's member galaxies, which shows that star formation was abruptly quenched 5 Gyr ago. MS 0451-03 will be an ideal target for future studies of the growth of structure along filaments, star-formation processes after a major merger, and the late-stage evolution of cluster collisions.