An overmassive Dark Halo around an Ultra-diffuse Galaxy in the Virgo Cluster

Understand

Ultra diffuse galaxies (UDGs) have the sizes of giant galaxies but the luminosities of dwarfs.

• A key to understanding their origins comes from their total masses, but their low surface brightnesses ($\mu(V) \geq$ 25.0) generally prohibit dynamical studies.
• Here we report the first such measurements for a UDG (VCC~1287 in the Virgo cluster), based on its globular cluster system dynamics and size.
• From 7 GCs we measure a mean systemic velocity $v_{\rm sys}$ = 1071$^{+14}_{-15}$ km/s, thereby confirming a Virgo-cluster association.