Reconciling mass-estimates of ultra-diffuse galaxies

Understand

The virial masses of ultra-diffuse galaxies (UDGs) have been estimated using the kinematics and abundance of their globular cluster populations, leading to disparate results.

• Some studies conclude that UDGs reside in massive dark matter halos while others, controversially, argue for the existence of UDGs with no dark matter at all.
• Here we show that these results arise because the uncertainties of these mass estimates have been substantially underestimated.
• Indeed, applying the same procedure to the well-studied Fornax dwarf spheroidal would conclude that it has an "overmassive" dark halo or, alternatively, that it lacks dark matter.