Constraints on Self-Interacting Fuzzy Dark Matter from the Stellar Kinematics of the Dwarf Galaxy Leo II

Abstract

The one-parameter fuzzy dark matter (FDM) model has faced increasingly stringent constraints from both Lyman-$\alpha$ forest observations and local measurements of dwarf galaxies. A natural extension to mitigate these limits is the inclusion of FDM self-interactions. In this study, we derive constraints in the two-dimensional parameter space $(m_a, f_a)$ using the dark matter density profile inferred from a Jeans analysis of the stellar kinematics in the dwarf galaxy Leo II, which has previously been employed to constrain non-interacting FDM. We find that, for a fixed particle mass $m_a$, attractive (repulsive) self-interaction leads to a more concentrated (more diffuse) FDM density profile relative to the non-interacting case, thereby improving (worsening) agreement with the Jeans analysis results. Our results indicate that, for either attractive or repulsive SI with strength $f_a^{-1}\lesssim 10^{-14}\,\mathrm{GeV}^{-1}$, the $95\%$ confidence-level lower limits on $m_a$ lies within the range $(1-10)\times10^{-22}\,\mathrm{eV}$, although the precise bounds depend to some extent on the statistical method employed. This analysis simultaneously constrains the two parameters $(m_a, f_a)$ without relying on assumptions about cosmological or galaxy evolution histories, and thus offers a complementary probe to existing constraints.