Abstract:

Massive Compact Halo Objects (MACHOs) remain a viable dark matter candidate that can be tested through their dynamical effects on stellar systems. In this talk, I will present how dynamical heating of stars in ultrafaint dwarf (UFD) galaxies provides powerful constraints on MACHOs across a broad mass range.
I will demonstrate the robustness of these bounds by conducting a comprehensive analysis that accounts for observational uncertainties in critical UFD parameters, including half-light radii, stellar velocity dispersions, total halo masses, and the shape of both dark matter and stellar density profiles. Applying this framework to well-established UFD candidates, I will show that multiple independent systems yield consistently strong limits in the mass range 10M⊙≲M≲10⁹M⊙, confirming and extending previous results based solely on Segue I.
I will also discuss exciting prospects from newly discovered systems, focusing on Ursa Major III/UNIONS 1. If confirmed as a bona fide UFD, this object would substantially improve existing constraints, yielding the strongest limits on MACHO dark matter in the intermediate mass range 1M⊙≲M≲10⁵M⊙.