Low metallicities and old ages for three ultra-diffuse galaxies in the Coma cluster

Meng Gu, Charlie Conroy, David Law, Pieter van Dokkum, Renbin Yan, David Wake, Kevin Bundy, Allison Merritt, Roberto Abraham, Jielai Zhang, Matthew Bershady, Dmitry Bizyaev, Jonathan Brinkmann, Niv Drory, Kathleen Grabowski, Karen Masters, Kaike Pan, John Parejko, Anne-Marie Weijmans, Kai Zhang