Abstract:
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 log(M∙/M⊙)<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 log(M∙)=8.32+4.08logσ*/200kms−1 , with an intrinsic scatter of σint = 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─104 M⊙ 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.
