Constrain the Dark Matter Distribution of Ultra-diffuse Galaxies with Globular-Cluster Mass Segregation: A Case Study with NGC5846-UDG1
Ultra-diffuse galaxies (UDGs) is very special. They have large core radii but low surface brightnesses. And large number of globular clusters (GCs) live inside them compared to normal galaxies. The most interesting thing is that they have much higher or lower dark matter masses compared to normal galaxies with the same stellar masses. Therefore, it triggered a frenzy of studies in recent years in the contexts of both understanding the formation of extreme galaxies and testing cosmology. The galaxy NGC5846-UDG1 (UDG1) serves as a remarkable example. Since it is well-observed except its dark matter properties, we aim to develop a semi-analytical model to constrain its dark matter properties.
To do that, I developed a semi-analytical model based on its progenitor SatGen considering tidal stripping, two-body relaxation, dynamical friction with some assumptions of initial condition for UDGs and GC population. A flowchart can be seen in Fig. 1. Finally, I combined the model with an MCMC inference tool, to derive constraints on the dark-matter halo of UDG1. By comparing with normal galaxies or normal relations, I found that UDG1 is DM deficient, low concentration system with rich GCs. It is the first time to constrain the DM properties of UDG1, which can be seen in Fig. 2. And this method is universal, which can be applied to other system as long as simple mass segregation is shown in observational data.
