Papers › The MUSE-Faint survey. II. The dark matter-density profile of the ultra-faint dwarf...
The MUSE-Faint survey. II. The dark matter-density profile of the ultra-faint dwarf galaxy Eridanus 2
Sebastiaan L. Zoutendijk, Jarle Brinchmann, Nicolas F. Bouché, Mark den Brok, Davor Krajnović, Konrad Kuijken, Michael V. Maseda, Joop Schaye
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Aims. We use stellar line-of-sight velocities to constrain the dark matter-density profile of Eridanus 2, an ultra-faint dwarf galaxy (M_V = -7.1, M_* ≈9 ×10⁴ M_⊙). We furthermore derive constraints on fundamental properties of self-interacting and fuzzy dark matter scenarios. Methods. We present new observations of Eridanus 2 from MUSE-Faint, a survey of ultra-faint dwarf galaxies with MUSE on the Very Large Telescope, and determine line-of-sight velocities for stars inside the half-light radius. Combined with literature data, we have 92 stellar tracers out to twice the half-light radius. We constrain models of cold dark matter, self-interacting dark matter, and fuzzy dark matter with these tracers, using CJAM and pyGravSphere for the dynamical analysis. Results. We find substantial evidence for cold dark matter over self-interacting dark matter and weak evidence for fuzzy dark matter over cold dark matter. We find a virial mass M₂₀₀ ∼10⁸ M_⊙ and astrophysical factors J(α_cᴶ) ∼10¹¹ M_⊙² kpc⁻⁵ and D(α_cᴰ) ∼10²-10^(2.5) M_⊙ kpc⁻². We do not resolve a core (r_c < 47 pc, 68-% level) or soliton (rₛₒₗ < 7.2 pc, 68-% level). These limits are equivalent to an effective self-interaction coefficient fΓ< 2.2 ×10⁻²⁹ cm³ s⁻¹ eV⁻¹ c² and a fuzzy-dark-matter particle mass mₐ > 4.0 ×10⁻²⁰ eV c⁻². The constraint on self-interaction is complementary to those from gamma-ray searches. The constraint on fuzzy-dark-matter particle mass is inconsistent with those obtained for larger dwarf galaxies, suggesting that the flattened density profiles of those galaxies are not caused by fuzzy dark matter. (Abridged)
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