Origins of ultra-diffuse galaxies in the Coma cluster II. Constraints from their stellar populations

Understand

In this second paper of the series, we study with new Keck/DEIMOS spectra the stellar populations of seven spectroscopically confirmed ultra-diffuse galaxies (UDGs) in the Coma cluster.

• We find intermediate to old ages (~ 7Gyr), low metallicities ([Z/H] ~ -0.7dex) and mostly super-solar abundance patterns ([Mg/Fe] ~ 0.13dex).
• These properties are similar to those of low-luminosity (dwarf) galaxies inhabiting the same area in the cluster and are most consistent with being the continuity of the stellar mass scaling relations of more massive galaxies.
• These UDGs' star formation histories imply a relatively recent infall into the Coma cluster, consistent with the theoretical predictions for a dwarf-like origin.