Tracing gaseous filaments connected to galaxy clusters: The case study of Abell 2744

¹ Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, 91405 Orsay, France
² Sorbonne Université, UMR7095, Institut d’Astrophysique de Paris, 98 bis Boulevard Arago, F-75014 Paris, France
³ Department of Astronomy, University of Geneva, Ch. d’Ecogia 16, 1290 Versoix, Switzerland
⁴ Université Claude Bernard Lyon 1, 69100 Villeurbanne, France
⁵ Laboratoire de Physique de l’École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, F-75005 Paris, France

^⋆ Corresponding author; stefano.gallo@universite-paris-saclay.fr

Received: 18 June 2024
Accepted: 25 October 2024

Abstract

Filaments connected to galaxy clusters are crucial environments for studying the build up of cosmic structures as they funnel matter towards the clusters’ deep gravitational potentials. Identifying gas in filaments is a challenge, due to their lower density contrast, which produces faint signals. Therefore, the best opportunity to detect these signals is in the outskirts of galaxy clusters. We revisited the X-ray observation of the cluster Abell 2744, using statistical estimators of the anisotropic matter distribution to identify filamentary patterns around it. We report, for the first time, the blind detection of filaments connected to a galaxy cluster from X-ray emission using a filament-finder technique and a multipole decomposition technique. We compare this result with filaments extracted from the distribution of spectroscopic galaxies using the same two approaches. This allowed us to demonstrate the robustness and reliability of our techniques in tracing the filamentary structure of three and five filaments connected to Abell 2744, in two and three dimensions, respectively.