A Supermassive Black Hole in an Ultracompact Dwarf Galaxy

Understand

Ultracompact dwarf galaxies (UCDs) are among the densest stellar systems in the universe.

• These systems have masses up to 200 million solar masses, but half light radii of just 3-50 parsecs.
• Dynamical mass estimates show that many UCDs are more massive than expected from their luminosity.
• It remains unclear whether these high dynamical mass estimates are due to the presence of supermassive black holes or result from a non-standard stellar initial mass function that causes the average stellar mass to be higher than expected.