Measuring the boson mass of fuzzy dark matter with stellar proper motions

TL;DR

This study assesses how future astrometric missions can measure fuzzy dark matter properties, specifically the boson mass and core radius, by analyzing stellar motions in dwarf galaxies to distinguish FDM from other dark matter models.

Contribution

It demonstrates that precise proper motion measurements of stars can constrain FDM boson mass and core size with high accuracy, aiding in confirming or refuting FDM as a dark matter candidate.

Findings

Proper motion of 2000+ stars can constrain boson mass and core radius to 3% accuracy.

Detection of the transition between solitonic core and NFW-like profile with 7% uncertainty.

Results can help resolve discrepancies between galactic and cosmological boson mass estimates.

Abstract

Fuzzy Dark Matter (FDM) is among the most suitable candidates to replace WIMPs and to resolve the puzzling mystery of dark matter. A galactic dark matter halo made of these ultralight bosonic particles leads to the formation of a solitonic core surrounded by quantum interference patterns that, on average, reproduce a Navarro-Frenk-White-like mass density profile in the outskirts of the halo. The structure of such a core is determined once the boson mass and the total mass of the halo are set. We investigated the capability of future astrometric Theia-like missions to detect the properties of such a halo within the FDM model, namely the boson mass and the core radius. To this aim, we built mock catalogs containing three-dimensional positions and velocities of stars within a target dwarf galaxy. We exploited these catalogs using a Markov Chain Monte Carlo algorithm and found that measuring the proper motion of at least 2000 stars within the target galaxy, with uncertainty $\sigma_v \leq 3$ km/s on the velocity components, will constrain the boson mass and the core radius with 3\% accuracy. Furthermore, the transition between the solitonic core and the outermost NFW-like density profile could be detected with an uncertainty of 7\%. Such results would not only help to confirm the existence of FDM, but they would also be useful for alleviating the current tension between galactic and cosmological estimations of the boson mass, or demonstrating the need for multiple particles with a broad mass spectrum as naturally arise String Axiverse.