2026ApJ...997..194A

We construct mass models of Milky Way dwarf spheroidal galaxies to place constraints on the central black hole masses they can host. We model the galaxies as a three-component system consisting of the stars, dark matter halo, and a central black hole, using the Osipkov-Merritt-Cuddeford class of the anisotropic distribution function. The posterior distribution of black hole mass remains flat toward the low-mass end, indicating that the kinematic data places an upper limit on the black hole mass. Our analysis yields a 95% credible upper limit of ${\mathrm{log}}({M}_{\bullet }/{M}_{\odot })\lt 6$. We combine our results with black hole mass measurements and upper limits from the literature to construct a unified M_•-σ_* relation spanning σ_* ∼ 10-300 km s^–1, described by ${\mathrm{log}}({M}_{\bullet })=8.32+4.08\,{\mathrm{log}}\left({\sigma }_{* }/200\,{\rm{km}}\,{{\rm{s}}}^{-1}\right)$, with an intrinsic scatter of σ_int = 0.55. We compare the inferred limits to models of black hole growth via momentum-driven accretion and stellar capture, which predict black hole masses in the range 10³-10⁴M_⊙ for the range σ_* ∼ 6-12 km s^–1, in close agreement with the M_•-σ_* relation within the 95% credible upper limits on the black hole masses derived in this work.