# Constrain the Dark Matter Distribution of Ultra-diffuse Galaxies with Globular-Cluster Mass Segregation: A Case Study with NGC5846-UDG1

**Authors:** Jinning Liang, Fangzhou Jiang, Shany Danieli, Andrew Benson, Phil Hopkins  
**arXiv:** [2304.14431](https://arxiv.org/abs/2304.14431)  
**Date:** 2023-04-27  
**Summary page:** https://www.summarizepaper.com/en/paper/2304.14431v1/

## Key points

- The study explores the potential of using globular clusters (GCs) to constrain the dark matter content of ultra-diffuse galaxies (UDGs).
- NGC5846-UDG1 is a UDG with a GC population that exhibits strong radial mass segregation, which indicates dynamical-friction-driven orbital decay.
- The authors develop a semi-analytical model of GC evolution to follow the effects of dynamical friction, tidal evolution, and two-body relaxation.
- Using Markov Chain Monte Carlo simulations, they forward-model the GCs in an NGC5846-UDG1-like potential to match observed GC mass, size, and spatial distributions while constraining the profile of the host halo and origin of the GCs.
- The results indicate that NGC5846-UDG1 is dark matter poor compared to what is expected from stellar to halo mass relations. Its halo concentration is low regardless of whether it has a cuspy or cored halo profile.
- Additionally, its GC population has an initial spatial distribution more extended than its smooth stellar distribution.
- These findings suggest caution against naively using the GC abundance halo mass relation to infer halo mass in UDGs.
- The authors provide their semi-analytical model as publicly available code applicable to other GC rich dwarf galaxies.

## Summary

This study explores the potential of using globular clusters (GCs) to constrain the dark matter content of ultra-diffuse galaxies (UDGs). Specifically, the authors focus on NGC5846-UDG1, a remarkable example of a UDG with a GC population that exhibits strong radial mass segregation. This mass segregation is indicative of dynamical-friction-driven orbital decay and opens up the possibility of using imaging data alone to constrain the dark-matter distribution in UDGs. To achieve this goal, the authors develop a semi-analytical model of GC evolution that starts from the initial mass function, initial structure-mass relation, and initial spatial distribution of GC progenitors. The model then follows the effects of dynamical friction, tidal evolution, and two-body relaxation. Using Markov Chain Monte Carlo simulations, they forward-model the GCs in an NGC5846-UDG1-like potential to match observed GC mass, size, and spatial distributions while constraining the profile of the host halo and origin of the GCs. The results indicate that NGC5846-UDG1 is dark matter poor compared to what is expected from stellar to halo mass relations. Its halo concentration is low regardless of whether it has a cuspy or cored halo profile. Additionally, its GC population has an initial spatial distribution more extended than its smooth stellar distribution. These findings suggest caution against naively using the GC abundance halo mass relation to infer halo mass in UDGs. The authors discuss their results in context with scaling laws for galaxy halo connections and provide their semi-analytical model as publicly available code applicable to other GC rich dwarf galaxies. In conclusion, this study presents a novel approach for constraining dark matter content in UDGs using their globular cluster populations' properties. The results highlight important considerations when inferring halo masses from GC abundances and provide a valuable tool for future studies of GC rich dwarf galaxies.