Weak-lensing Analysis of Intracluster Filaments in Abell 2744: Matched-filter Scans and Stepwise 2D Tracing

Abstract

We present a weak-lensing (WL) analysis of filamentary structures in the merging galaxy cluster Abell 2744 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 re-characterizing 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.

22 pages, 13 figures; submitted to ApJ