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Adaptive Reconstruction of Cluster Halos (ARCH): Integrating Shear and Flexion for Substructure Detection
Journal article   Open access   Peer reviewed

Adaptive Reconstruction of Cluster Halos (ARCH): Integrating Shear and Flexion for Substructure Detection

Jacob Shpiece and David M Goldberg
The Astrophysical journal, v 1003(2), 171
01 Jun 2026
url
https://doi.org/10.3847/1538-4357/ae681aView
Published, Version of Record (VoR) Open

Abstract

Bayesian analysis Clusters Gravitational lenses Halos Local optimization Reconstruction Resampling Shear Statistical inference Uncertainty
We present Adaptive Reconstruction of Cluster Halos (ARCH), a new gravitational lensing pipeline for cluster mass reconstruction that applies a joint shear-flexion analysis to JWST imaging. Previous approaches have explored joint shear+flexion reconstructions through forward modeling and Bayesian inference frameworks; in contrast, ARCH adopts a staged optimization strategy that incrementally filters and selects candidate halos rather than requiring a global likelihood model or strong priors. This design makes reconstructions computationally tractable and flexible, enabling systematic tests of multiple signal combinations within a unified framework. ARCH employs staged candidate generation, local optimization, filtering, forward selection, and global strength refinement, with a combined fit metric weighted by per-signal uncertainties. Applied to A2744 and El Gordo, the pipeline recovers convergence maps and subcluster masses consistent with published weak+strong lensing results. In A2744, the central core mass within 300 h−1 kpc is 2.1 × 1014 M⊙h−1, while in El Gordo, the northwestern and southeastern clumps are recovered at 2.6 × 1014 M⊙h−1 and 2.3 × 1014 M⊙h−1. Jackknife resampling indicates typical 1σ uncertainties of 1012–1013 M⊙h−1, with the all-signal and shear+ F reconstructions providing the most stable results. These results demonstrate that flexion, when anchored by shear, enhances sensitivity to cluster substructure while maintaining stable cluster-scale mass recovery.

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