Weak-Lensing Detection of Intercluster Filaments in Three Nearby Cluster Systems

Abstract

Direct detection of intercluster filaments is challenging due to their low surface density, resulting in a weak deflection field. We present weak-lensing detections of intercluster filaments using wide-field Dark Energy Camera (DECam) observations from the Local Volume Complete Cluster Survey (LoVoCCS). A matched-filter method was applied to identify filamentary structures in three nearby ($z < 0.1$) systems centered on Abell 401, Abell 2029, and Abell 3558. We discover two prominent filaments ($\geq 4\sigma$) in each system, with the strongest detections ($6.4\sigma - 7.3\sigma$) around Abell 401 and Abell 2029. In particular, we report the first robust weak-lensing detections $(>5 \sigma)$ of the intercluster bridges connecting the cluster pairs Abell 401/399, Abell 2029/2033, Abell 2029/SIG, and Abell 3558/3556. Adopting a filament convergence model motivated by numerical simulations, we infer the maximum convergence ($\kappa_0$) and characteristic width ($h_{\mathrm{c}}$) for all six filaments, yielding $\kappa_0 \sim 0.015 - 0.053$ and $h_{\mathrm{c}} \sim 0.11 - 0.45 \ \mathrm{Mpc}$. The performance of the matched-filter technique is validated using mock shear catalogs and further tested on a null field around Abell 2351. We also explore the potential of using the B-mode lensing signal of filaments to suppress cluster-induced shear contamination. These results demonstrate the feasibility of directly mapping dark matter filaments with current and future wide-field weak-lensing datasets.