The influence of the Cosmic Web on the properties of dwarf galaxies in the Fornax-Eridanus Supercluster

Abstract

We analyze a sample of low surface brightness dwarf galaxies (mu_e,g > 24.2 mag arcsec^-2), detected using interpretable machine learning tools from the DES survey. We use the Tanoglidis et al. (2021) sample, identified with machine learning, supplemented by Thuruthipilly et al. (2024). We focus on the Fornax-Eridanus Supercluster, where our group determined its 3D filamentary spine using massive galaxies. We study the effect of the large-scale environment on dwarfs in the Fornax-Eridanus Complex. To do this, we compare the properties of dwarfs in clusters, groups, and the field, and examine how these properties vary with distance to the spine of the Fornax Wall. We check if dwarfs trace the Fornax Wall spine, defined by massive galaxies. We identify Fornax Wall members from our photometric dwarf catalog, dividing them into i) within one virial radius of a galaxy group or cluster and ii) outside this radius (field galaxies). We assume dwarfs near the Fornax Wall are at the same distance as the massive galaxies. We then study their distribution within the complex. We probe the morphology-density relation and examine galaxy properties versus distance from the Fornax Wall spine. Red dwarfs are mostly in or near groups close to the Fornax Wall, dominating the population, while blue dwarfs dominate the field. Larger-sized red dwarfs tend to reside in group environments, with significantly larger effective radii than those in the field. 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 dwarfs. Mass density distribution in field and group/cluster is similar, indicating the group/cluster population could be an aged version of the field. The group/cluster objects with excess sizes must have been made through interactions in the groups/clusters.

Figures (22)

• Figure 1: The Fornax Eridanus (FE) Supercluster: The gray line traces the 2D projection of the filaments that form the Fornax Wall spine (R24). Green circles and their corresponding labels represent the Fornax Wall groups (R24, Tempel2016-galgroupcat) and their virial radii (Kourkchi2017). Gray points are the brightest galaxies in clusters and in groups. The Eridanus Supergroup, Fornax cluster and the Dorado group are highlighted with different colours. The dotted-line is the DES footprint of T21 and T24, which encloses nearly all of the Fornax Wall.
• Figure 2: colour-magnitude diagram of group dwarfs (top; orange for T21 and green for T24) and field dwarfs (bottom; orange for T21 and green for T24). Background galaxies removed using colour selection (red), using surface brightness-magnitude diagram (pink; see Section 3.1.4) are included. The gray shaded region is the region removed by the $g - r$ colour selection. Fornax cluster dwarf galaxies from Su2021 are plotted to highlight the red-sequence (black).
• Figure 3: Surface brightness-magnitude diagram of field dwarfs (T21: dots, T24: crosses) with $g - r$ colour in the colourbar. The linear least squares fit of the diagram is included as the black line. The dotted line is 3$\sigma$ away from the fit towards high surface brightness.
• Figure 4: Virial radii of the groups in the Fornax-Eridanus Supercluster region, including Fornax Wall groups (black circle), background and foreground groups with distances outside the 15 - 30 Mpc h$^{-1}$ range (red circle). The background and foreground groups within 2 times the virial radius of Fornax Wall groups and 1 deg around massive galaxies (green cross). Also shown are objects removed manually (red points), brightest group members in the Fornax Wall from R24 (purple points) and dwarfs from the T21 catalogue after background galaxy removal through scaling relation (gray points), and dwarfs from the T24 catalogue (blue points) are also included.
• Figure 5: Massive galaxies in the Fornax Wall with their comoving distances from Tempel2016-galgroupcat in the colourbar. Black circles are the Fornax Wall groups. Dotted lines separate the Wall into segments which are labelled with numbers.