Hubble Frontier Fields: The Geometry and Dynamics of the Massive Galaxy Cluster Merger MACSJ0416.1-2403 [Replacement]
We use a joint optical/X-ray analysis to constrain the geometry and history of the ongoing merging event in the massive galaxy cluster MACSJ0416.1-2403 (z=0.397). Our investigation of cluster substructure rests primarily on a strong and weak lensing mass reconstruction based on the deep, high-resolution images obtained for the HFF initiative. To reveal the system’s dynamics, we complement this lensing analysis with a study of the intra-cluster gas using Chandra data, and a 3D model of the distribution and motions of cluster galaxies derived from >100 spectroscopic redshifts. The multi-scale grid model obtained from our combined weak and strong lensing analysis extends high-precision mass reconstruction for the cluster core to cluster-centric distances of almost 1 Mpc. Our analysis detects the two well known mass concentrations near the centre of the field. A pronounced offset between collisional and collisionless matter is only observed for the SW cluster component, while excellent alignment is found for the NE cluster. Both the lensing analysis and the distribution of cluster light strongly suggest the presence of a third massive structure, almost 2arcmin SW of the cluster centre. Since no X-ray emission is detected in this region, we conclude that this structure is non-virialised and speculate that it might be part of a large-scale filament that is almost aligned with our line of sight. Combining all evidence from the distribution of dark and luminous matter, we propose two alternative scenarios for the trajectories of the components of MACSJ0416.1-2403 (one pre-, the other post-collision), a merger that features a significant impact parameter and is proceeding along an axis that is highly inclined with respect to the plane of the sky.