Frontier Fields: Subaru Weak-Lensing Analysis of the Merging Galaxy Cluster A2744

Abstract

We present a weak-lensing analysis of the merging {\em Frontier Fields} (FF) cluster Abell~2744 using new Subaru/Suprime-Cam imaging. The wide-field lensing mass distribution reveals this cluster is comprised of four distinct substructures. Simultaneously modeling the two-dimensional reduced shear field using a combination of a Navarro--Frenk--White (NFW) model for the main core and truncated NFW models for the subhalos, we determine their masses and locations. The total mass of the system is constrained as $M_{200c}=(2.06\pm 0.42)\times 10^{15}{M}_{\odot }$. The most massive clump is the southern component with $M_{200c}=(7.7\pm 3.4)\times 10^{14}{M}_{\odot }$, followed by the western substructure ($M_{200c}=(4.5\pm 2.0)\times 10^{14}{M}_{\odot }$) and two smaller substructures to the northeast ($M_{200c}=(2.8\pm 1.6)\times 10^{14}{M}_{\odot }$) and northwest ($M_{200c}=(1.9\pm 1.2)\times 10^{14}{M}_{\odot }$). The presence of the four substructures supports the picture of multiple mergers. Using a composite of hydrodynamical binary simulations we explain this complicated system without the need for a "slingshot" effect to produce the northwest X-ray interloper, as previously proposed. The locations of the substructures appear to be offset from both the gas ($87_{-28}^{+34}$ arcsec, 90\% CL) and the galaxies ($72_{-53}^{+34}$ arcsec, 90\% CL) in the case of the northwestern and western subhalos. To confirm or refute these findings, high resolution space-based observations extending beyond the current FF limited coverage to the west and northwestern area are essential.

17 pages, 10 figures, 6 tables; ApJ accepted version; Textual edits, minor clarifications and some discussion added