The role of supercluster filaments in shaping galaxy clusters

¹ Departamento de Física, Universidad Técnica Federico Santa María, Avenida España, 1680 Valparaíso, Chile
² Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla, 4059 Valparaíso, Chile
³ Millennium Nucleus for Galaxies (MINGAL), Valparaíso, Chile
⁴ Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2, 00560 Helsinki, Finland
⁵ Instituto de Astronomía y Ciencias Planetarias (INCT), Universidad de Atacama, Copayapu, 485 Copiapó, Chile
⁶ INAF – Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Napoli, Italy
⁷ Departamento de Astronomía, Universidad de La Serena, Avda. Raúl Bitrán, 1305 La Serena, Chile
⁸ School of Physics & Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
⁹ Departamento de Física Teórica y del Cosmos, Edificio Mecenas, Campus Fuentenueva, Universidad de Granada, E-18071 Granada, Spain
¹⁰ Instituto Universitario Carlos I de Física Teórica y Computacional, Universidad de Granada, 18071 Granada, Spain
¹¹ Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro, RJ, Brazil
¹² Max-Planck-Institut für extraterrestrische Physik (MPE), Gießenbachstraße 1, 85748 Garching bei München, Germany
¹³ Institute of Astrophysics, Facultad de Ciencias Exactas, Universidad Andrés Bello, Sede Concepción, Talcahuano, Chile
¹⁴ Instituto de Astrofísica de La Plata, CONICET-UNLP, Paseo del Bosque s/n, B1900FWA La Plata, Argentina
¹⁵ Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, B1900FWA La Plata, Argentina
¹⁶ Departamento de Astronomia, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão 1226, Cidade Universitária, São Paulo 05508-090, Brazil
¹⁷ School of Computer Science, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
¹⁸ Observatório do Valongo, Ladeira Pedro António, 43, Saúde, Rio de Janeiro, 20080-090 BR, Brazil
¹⁹ Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW, 2006 Sydney, Australia
²⁰ Centre of Excellence for Data Science, Artificial Intelligence & Modelling, The University of Hull, Cottingham Road, KingstonUpon-Hull HU6 7RX, UK
²¹ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, United Kingdom
²² Kuffner Observatory, Johann-Staud-Straße 10, 1160 Vienna, Austria
²³ Laboratório Nacional de Astrofísica (LNA/MCTI), Rua Estados Unidos, 154, Itajubá 37504-364, Brazil
²⁴ Instituto de Física y Astronomía, Universidad de Valparaíso, Avda. Gran Bretaña 1111, Valparaíso, Chile
²⁵ Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
²⁶ INAF-Padova Astronomical Observatory, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
²⁷ Departamento de Tecnologías Industriales, Facultad de Ingeniería, Universidad de Talca, Los Niches km 1, Curicó, Chile
²⁸ Universidade Presbiteriana Mackenzie, R. da Consolaçao, 930 -Consolaçao, São Paulo, Brazil
²⁹ European Southern Observatory, Science Operations, Alonso de Cordova 3107, Vitacura, 19001 Santiago, Chile
³⁰ Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Toruń, Poland
³¹ Univ Lyon, Ens de Lyon, Univ Lyon1, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, F–69007 Lyon, France

^★ Corresponding author: rbaier@usm.cl

Received: 23 August 2025
Accepted: 5 October 2025

Abstract

Context. In a hierarchical ΛCDM Universe, cosmic filaments serve as the primary channels for matter accretion into galaxy clusters, influencing the shape of their dark matter halos.

Aims. We investigate whether the elongation of galaxy clusters correlates with the orientation of surrounding filaments, providing the first observational test of this relationship in large supercluster regions.

Methods. We identified and characterized cosmic filaments in two dimensions within the two superclusters that are part of the low-redshift sub-survey of the Chilean Cluster Galaxy Evolution Survey (CHANCES): the Shapley supercluster and the Horologium-Reticulum supercluster. We analyzed the alignment between filament directions–traced by galaxy distributions–and the triaxiality of cluster gravitational potentials–traced by X-ray emission–using publicly available optical and X-ray data.

Results We have found that most (82%) of the X-ray clusters are associated with and interconnected by the optically detected filaments. The clusters-filaments alignment analysis shows that the elongation of most clusters is well aligned with nearby filaments, providing observational confirmation of theoretical predictions, with the alignment progressively reducing at larger cluster-centric distances (> 1.6r₂₀₀).

Conclusions. Overall, our results support the notion that filaments are the main source of galaxy accretion at redshift below 0.1, and additionally provide evidence that matter accretion through filaments shapes the gravitational potential of galaxy clusters. We propose this measurement as a simple observational proxy to determine the direction of accretion in clusters, which is key to understanding both galaxy evolution and the merger history of galaxy clusters.