# The morphological mix of dwarf galaxies in the nearby Universe

**Authors:** Ilin Lazar, Sugata Kaviraj, Aaron E. Watkins, Garreth Martin, Brian Bichang'a, Ryan A. Jackson  
**arXiv:** [2402.12440](https://arxiv.org/abs/2402.12440)  
**Date:** 2024-02-19  
**Summary page:** https://www.summarizepaper.com/en/paper/2402.12440v1/

## Key points

- Study focuses on census of dwarf galaxies in low-density environments outside local neighborhood
- Utilizes sample of 257 dwarf galaxies with stellar masses ranging from 10^8 MSun to 10^9.5 MSun at redshifts less than 0.08
- Identifies three principal morphological classes among dwarf galaxies: early-type (elliptical/S0), late-type (spiral), and featureless
- Reveals that 43% exhibit traditional 'early-type' morphology, 45% exhibit 'late-type' morphology, and 10% belong to a 'featureless' class
- Interactions play significant role in around 20% of overall star formation activity in dwarf population, with evidence present for each morphological class
- Differences observed between dwarf early-types and massive counterparts suggest distinct formation histories influenced by secular processes rather than interactions
- Featureless dwarfs in low-density environments may be formed through internal baryonic feedback rather than environmental processes
- Distinguishing between early and late-type dwarfs using traditional morphological parameters proves challenging unlike in the massive-galaxy regime

## Summary

This study provides a detailed census of the morphological mix of dwarf galaxies in low-density environments outside the local neighborhood. The research utilizes a complete and unbiased sample of 257 dwarf galaxies with stellar masses ranging from 10^8 MSun to 10^9.5 MSun at redshifts less than 0.08. Through visual inspection of deep optical images and their unsharp-masked counterparts, three principal morphological classes are identified among dwarf galaxies: early-type (elliptical/S0), late-type (spiral), and featureless. Interestingly, 10% of dwarfs belong to a 'featureless' class that lacks central light concentration seen in early-types or any spiral structure - a class not observed in massive galaxies. The analysis reveals that 43% and 45% of dwarfs exhibit traditional 'early-type' and 'late-type' morphologies respectively. Additionally, interactions are found to play a significant role in around 20% of overall star formation activity in the dwarf population, with evidence present in different proportions for each morphological class. Comparing dwarf early-types to their massive counterparts reveals differences in interaction incidence and concentration levels, suggesting distinct formation histories influenced by secular processes rather than interactions for dwarf early-types. Furthermore, the absence of large groups or clusters at z < 0.08 in COSMOS indicates that featureless dwarfs in low-density environments may be formed through internal baryonic feedback rather than environmental processes. While interacting dwarfs can be identified using asymmetry parameters, distinguishing between early and late-type dwarfs using traditional morphological parameters like CAS, M20, and the Gini coefficient proves challenging unlike in the massive-galaxy regime. This paper is organized into sections detailing datasets used for analysis, exploration of dwarf morphology through visual inspection and morphological parameters comparison with massive galaxies. The findings shed light on the evolution of different dwarf morphological classes within low-density environments outside our local neighborhood.