# Further evidence for a population of dark-matter-deficient dwarf galaxies

## TL;DR

This paper presents evidence for a population of dwarf galaxies that appear to be dominated by baryons rather than dark matter, challenging standard cosmological models of galaxy formation.

## Contribution

It reports 19 dwarf galaxies with baryon dominance beyond their half-light radii, including 14 isolated ones, providing new observational evidence against existing dark matter dominance assumptions.

## Key findings

- 19 dwarf galaxies with baryon-dominated outskirts
- 14 isolated dwarf galaxies free from environmental effects
- Challenges to standard galaxy formation theories

## Abstract

In the standard cosmological model, dark matter drives the structure formation and constructs potential wells within which galaxies may form. The baryon fraction in dark halos can reach the universal value (15.7%) in massive clusters and decreases rapidly as the mass of the system decreases. The formation of dwarf galaxies is sensitive both to baryonic processes and the properties of dark matter owing to the shallow potential wells in which they form. In dwarf galaxies in the Local Group, dark matter dominates the mass content even within their optical-light half-radii (r_e ~ 1 kpc). However, recently it has been argued that not all dwarf galaxies are dominated by dark matter. Here we report 19 dwarf galaxies that could consist mainly of baryons up to radii well beyond r_e, at which point they are expected to be dominated by dark matter. Of these, 14 are isolated dwarf galaxies, free from the influence of nearby bright galaxies and high dense environments. This result provides observational evidence that could challenge the formation theory of low-mass galaxies within the framework of standard cosmology. Further observations, in particular deep imaging and spatially-resolved kinematics, are needed to constrain the baryon fraction better in such galaxies.