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

Jinning Liang, Fangzhou Jiang, Shany Danieli, Andrew Benson, Phil Hopkins

| Summary:

[[{“value”:”The properties of globular clusters (GCs) contain valuable information of
their host galaxies and dark-matter halos. In the remarkable example of
ultra-diffuse galaxy, NGC5846-UDG1, the GC population exhibits strong radial
mass segregation, indicative of dynamical-friction-driven orbital decay, which
opens the possibility of using imaging data alone to constrain the dark-matter
content of the galaxy. To explore this possibility, we develop a
semi-analytical model of GC evolution, which starts from the initial mass
function, the initial structure-mass relation, and the initial spatial
distribution of the GC progenitors, and follows the effects of dynamical
friction, tidal evolution, and two-body relaxation. Using Markov Chain Monte
Carlo, we forward-model the GCs in a NGC5846-UDG1-like potential to match the
observed GC mass, size, and spatial distributions, and to constrain the profile
of the host halo and the origin of the GCs. We find that, with the assumptions
of zero mass segregation when the star clusters were born, NGC5846-UDG1 is
relatively dark-matter poor compared to what is expected from
stellar-to-halo-mass relations, and its halo concentration is lower than the
cosmological average, irrespective of having a cuspy or a cored profile. Its GC
population has an initial spatial distribution more extended than the smooth
stellar distribution. We discuss the results in the context of scaling laws of
galaxy-halo connections, and warn against naively using the
GC-abundance-halo-mass relation to infer the halo mass of UDGs. Our model is
generally applicable to GC-rich dwarf galaxies, and is publicly available at
https://github.com/JiangFangzhou/GCevo.”}]] 

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