Fuzzy Dark Matter and the Impact of Core-Halo Diversity on Its Particle Mass Constraints

Abstract

We investigate how diversity in the core-halo mass relation affects constraints on the fuzzy dark matter particle mass $m_\psi$ inferred from the internal kinematics of dwarf galaxies, and how these constraints are impacted by the inclusion of higher-order stellar velocity moments. Using stellar line-of-sight velocities and projected positions for eight Milky Way dwarf spheroidal galaxies, we model their dark matter halos as solitonic cores embedded within outer NFW envelopes. We apply both second- and fourth-order Jeans analyses to derive the posterior distribution of $m_\psi$. Our results show that there are two ranges of $m_\psi$ consistent with the observed kinematics: $\log_{10}(m_\psi/\mathrm{eV}) = -19.79^{+0.60}_{-0.53}$, and a narrower small-mass window $\log_{10}(m_\psi/\mathrm{eV}) = -21.82^{+0.35}_{-0.26}$, both within the 68% credible intervals. The latter becomes prominent only when core-halo diversity is taken into account, which highlights the sensitivity of the inferred fuzzy dark matter particle mass constraints to our understanding of the core-halo relation. Future observations, providing larger stellar samples and more precise kinematic measurements, will be essential for clarifying the allowed parameter space of fuzzy dark matter.