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

Abstract

We present a weak-lensing analysis of the merging 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}<SUB>200{{c</SUB>}}=(2.06+/- 0.42)× {10}<SUP>15</SUP> {M}<SUB>☉ </SUB>. The most massive clump is the southern component with {M}<SUB>200{{c</SUB>}}=(7.7+/- 3.4)× {10}<SUP>14</SUP> {M}<SUB>☉ </SUB>, followed by the western substructure ({M}<SUB>200{{c</SUB>}}=(4.5+/- 2.0)× {10}<SUP>14</SUP> {M}<SUB>☉ </SUB>) and two smaller substructures to the northeast ({M}<SUB>200{{c</SUB>}}=(2.8+/- 1.6)× {10}<SUP>14</SUP> {M}<SUB>☉ </SUB>) and northwest ({M}<SUB>200{{c</SUB>}}=(1.9+/- 1.2)× {10}<SUP>14</SUP> {M}<SUB>☉ </SUB>). 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}<SUB>-28</SUB><SUP>+34</SUP> arcsec, 90% CL) and the galaxies ({72}<SUB>-53</SUB><SUP>+34</SUP> 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. Based in part on data collected at the Subaru Telescope, which is operated by the National Astronomical Society of Japan.