# How nucleation and luminosity shape faint dwarf galaxies

## TL;DR

This study investigates the shapes of faint quiescent dwarf galaxies in clusters, revealing that nucleation and luminosity influence their thickness, with nucleated galaxies being thicker and suggesting early formation history.

## Contribution

It demonstrates that nucleation and luminosity significantly affect galaxy shape, and environment has minimal impact once these factors are considered.

## Key findings

- Nucleated satellites are thicker than non-nucleated ones across all luminosities.
- Fainter galaxies are systematically thicker regardless of nucleation.
- Environment does not significantly influence the three-dimensional structure after accounting for nucleation.

## Abstract

We study the intrinsic shapes of a sample of over 400 quiescent galaxies in the cores of the Virgo and Fornax clusters with luminosities $10^{6} \leq L_{g}/L_{\odot} \leq 10^{8}$. Similar to satellites of the Local Group and Centaurus A, these faint, low surface brightness cluster galaxies are best described as a family of thick ($C/A > 0.5$), oblate-triaxial spheroids. However, the large sample size allows us to show that the flattening of their stellar distributions depends both on luminosity and on the presence of a nuclear star cluster. Nucleated satellites are thicker at all luminosities compared to their non-nucleated counterparts, and fainter galaxies are systematically thicker as well, regardless of nucleation. Once nucleation is accounted for, we find no evidence that the environment the satellites live in plays a relevant role in setting their three-dimensional structure. We interpret both the presence of stellar nuclei and the associated thicker shapes as the result of preferential early and rapid formation, effectively making these faint nucleated galaxies the first generation of cluster satellites.