Constraining Ultra Light Dark Matter with the Galactic Nuclear Star Cluster

TL;DR

This study uses the Milky Way's nuclear star cluster to constrain ultra-light dark matter models by testing for the presence of a soliton core, leading to exclusion of certain dark matter particle masses.

Contribution

First application of dynamical modeling of the Galactic center to constrain ultra-light dark matter particle mass using the nuclear star cluster data.

Findings

Excluded ULDM particle masses between 10^{-20.4} and 10^{-18.5} eV.

Demonstrated sensitivity of the NSC to specific ULDM mass ranges.

Validated methodology with mock data.

Abstract

We use the Milky Way's nuclear star cluster (NSC) to test the existence of a dark matter 'soliton core', as predicted in ultra-light dark matter (ULDM) models. Since the soliton core size is proportional to mDM^{-1}, while the core density grows as mDM^{2}, the NSC (dominant stellar component within about 3 pc) is sensitive to a specific window in the dark matter particle mass, mDM. We apply a spherical isotropic Jeans model to fit the NSC line-of-sight velocity dispersion data, assuming priors on the precisely measured Milky Way's supermassive black hole (SMBH) mass and the well-measured NSC density profile. We find that the current observational data reject the existence of a soliton core for a single ULDM particle with mass in the range 10^{-20.4} < mDM < 10^{-18.5} eV, assuming that the soliton core structure is not affected by the Milky Way's SMBH. We test our methodology on mock data, confirming that we are sensitive to the same range in ULDM mass as for the real data. Dynamical modelling of a larger region of the Galactic centre, including the nuclear stellar disc, promises tighter constraints over a broader range of mDM. We will consider this in future work.