Weak-lensing Analysis of Intracluster Filaments in A2744: Matched-filter Scans and Stepwise 2D Tracing
October 2026 • 2026ApJ..1009...93C
Abstract • We present a weak-lensing (WL) analysis of filamentary structures in the merging galaxy cluster A2744 using wide-field Magellan/MegaCam imaging data. We employ two complementary techniques: standard matched-filter scans to identify global orientations and a new stepwise 2D tracing method to reconstruct locally varying filament orientations. The matched-filter analysis detects coherent filamentary features in the northwest and east directions across both inner (1.0--2.2 Mpc) and outer (2.2--3.4 Mpc) annuli. However, while the northwest filament yields consistent constraints across both regions, parameter inference for the eastern structure remains unstable and radially inconsistent when using the fiducial reference point. Additional matched-filter scans centered on the three lensing mass peaks show that the inferred directions depend on the adopted reference point. We demonstrate that recharacterizing the eastern structure using the locally preferred stepwise-traced direction significantly resolves these tensions, improving fit quality and bringing inner and outer constraints into agreement. These results show that stepwise 2D tracing complements global matched-filter scans by tracing locally coherent directions without requiring the full structure to pass through a single predefined point. Furthermore, the detected filaments align well with diffuse X-ray structures and previously identified merger axes, supporting their physical connection to the cluster's mass assembly.
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