First constraints on Fuzzy Dark Matter from the dynamics of stellar streams in the Milky Way

TL;DR

This paper introduces a new method to constrain ultra-light bosonic dark matter by analyzing the perturbations in stellar streams caused by Fuzzy Dark Matter's turbulent density field, providing a lower mass limit.

Contribution

The authors develop a novel dynamical approach using stellar stream thickening to set constraints on Fuzzy Dark Matter particle mass, complementing existing methods.

Findings

Derived a conservative lower limit for boson mass: $m_a > 1.5 imes 10^{-22}$ eV.

Showed that FDM-induced perturbations are observable in stellar streams within the relevant mass range.

Demonstrated the potential of this method as an independent probe of FDM.

Abstract

We present a novel method to constrain the mass of ultra-light bosons as the dark matter using stellar streams formed by disrupting Globular Clusters in the Milky Way. The turbulent density field of Fuzzy Dark Matter (FDM) haloes results in perturbations and dynamical heating of thin streams. Using numerical simulations based on an effective model, we explore the magnitude of this phenomenon and show that this is observable for the range of axion masses $m_a$ that is interesting for alleviating the `small-scale problems' of $\Lambda$CDM. We derive an analytical model for the thickening of thin stellar streams and obtain an early conservative lower limit for the boson mass of $m_a > 1.5 \times 10^{-22}~$eV, using pre-Gaia literature data for six Milky Way streams and after marginalizing over physical parameters. This demonstrates the great promise for using this novel dynamical method as a fully independent probe of FDM, to complement results based on Lyman-$\alpha$ forest data.