The influence of the cosmic web on the properties of dwarf galaxies in the Fornax-Eridanus supercluster

¹ Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV, Groningen, The Netherlands
² Instituto de Astrofísica de Canarias, Vía Láctea S/N, E-38205 La Laguna, Spain
³ Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA, Leiden, The Netherlands
⁴ Departamento de Fisica, Universidad Tecnica Federico Santa Maria, Avenida España 1680 Valparaíso, Chile
⁵ Millennium Nucleus for Galaxies (MINGAL), Valparaíso, Chile

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 25 September 2025
Accepted: 25 March 2026

Abstract

Context. In this paper, we analyse a sample of low surface brightness dwarf galaxies with a mean effective surface brightness of μ̅_e,g > 24.2 mag arcsec⁻², detected using interpretable machine learning tools from the DES survey, and study their properties as a function of their position within the cosmic web to understand the role that the cosmic web plays in the evolution of dwarf galaxies. Given their diffuse nature, dwarf galaxies are particularly well suited for examining environmental effects, which can impact their morphology and structure. We used two samples of dwarf galaxies in which a large number of objects were identified using machine learning techniques. We note that these samples likely contain a significant percentage of false positives; however, they represent the best sample currently available for this work. We concentrated on the Fornax–Eridanus supercluster area, where our group recently determined the 3D filamentary spine (or central axis) of the supercluster using massive galaxies in this area.

Aims. Our objective is to explore the effect of the large-scale environment on dwarf galaxies in the Fornax–Eridanus complex. To do this, we compared the properties of dwarfs in clusters, groups, and the field and examined how these properties change as a function of distance to the spine of the Fornax Wall. In particular, we investigated whether dwarfs trace the Fornax Wall spine, which has been defined by massive galaxies.

Methods. We first identified members of the Fornax Wall from our photometric dwarf galaxy catalogue and divided the population into two groups: i) those within one virial radius of a galaxy group or cluster and ii) those outside this radius (field galaxies). We assumed that the dwarf galaxies near the Fornax Wall are at the same distance as the massive galaxies in the wall. We then studied their distribution within the complex. We probed the morphology-density relation and examined galaxy properties such as effective radius, surface brightness, Sérsic index, colour, and stellar mass with respect to their distance from the spine of the Fornax Wall.

Results. Our findings show that red dwarfs are located mostly in and near groups close to the Fornax Wall, where they dominate the population, while blue dwarfs dominate in the field environment. We find that the larger-sized red dwarf galaxies tend to reside in group environments, with significantly larger effective radii compared to their counterparts in the field. Furthermore, red dwarfs are more concentrated towards the Fornax Wall than blue dwarfs. This suggests that the group environment plays a significant role in the evolution of dwarf galaxies. We find that the mass density distribution in the field and in galaxy groups or clusters is similar, indicating that the population in groups or clusters could be an aged version of the field. The galaxies in groups or clusters with excess sizes must have been made through interactions within these environments. This work lays the foundation for future studies that explore, in detail, the importance of local and large-scale environments in the formation and evolution of dwarfs.