# Testing $\Lambda$CDM With Dwarf Galaxy Morphology

## TL;DR

This study compares observed dwarf galaxy shapes with CDM simulation predictions, finding discrepancies that suggest the need for alternative dark matter models if oblate morphologies are confirmed.

## Contribution

It introduces a method to infer 3D shapes of dwarf galaxies and highlights potential conflicts with CDM simulations based on observed morphologies.

## Key findings

- Oblate shapes observed in high mass-to-light ratio dwarf galaxies.
- Prolate shapes in low mass-to-light ratio dwarf galaxies.
- Discrepancy between observed shapes and CDM simulation predictions.

## Abstract

The leading tensions to the collisionless cold dark matter (CDM) paradigm are the "small-scale controversies", discrepancies between observations at the dwarf-galactic scale and their simulational counterparts. In this work we consider methods to infer 3D morphological information on Local Group dwarf spheroidals, and test the fitness of CDM+hydrodynamics simulations to the observed galaxy shapes. We find that the subpopulation of dwarf galaxies with mass-to-light ratio $\gtrsim 100 M_\odot/L_\odot$ reflects an oblate morphology. This is discrepant with the dwarf galaxies with mass-to-light ratio $\lesssim 100 M_\odot/L_\odot$, which reflect prolate morphologies, and more importantly with simulations of CDM-sourced galaxies which are explicitly prolate. Although more simulations and data are called for, if evidence of oblate pressure-supported stellar distributions persists, we argue that an underlying oblate non-CDM dark matter halo may be required, and present this as motivation for future studies.