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

TL;DR

This paper introduces a new stepwise 2D tracing method for weak-lensing analysis of filamentary structures in galaxy clusters, improving the detection and characterization of complex filaments.

Contribution

The study develops and applies a novel stepwise 2D tracing technique that enhances filament detection accuracy over traditional global scans.

Findings

Detected coherent filaments in Abell 2744 aligned with X-ray structures.

Re-characterizing filaments locally resolves parameter inconsistencies.

Stepwise tracing improves filament analysis in complex cluster environments.

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 restricted to global reference-point scans. We demonstrate that re-characterizing the eastern structure using the locally preferred elongation directions from our stepwise tracer significantly resolves these tensions, improving fit quality and bringing inner and outer constraints into agreement. 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. These results highlight that stepwise 2D tracing is essential for characterizing curved or complex filaments where global reference-point scans are insufficient.