Abstract

Recent observations have shown that Ultra-Diffuse Galaxies (UDGs, which have the luminosities of dwarfs but sizes of giant galaxies) are surprisingly abundant in local clusters of galaxies. The origin of UDGs remains unclear, as the interpretation of these studies has been hindered by the (partly) subjective selection of these galaxies, and the limited study of only the Coma and Virgo clusters. I’ll present results of the first systematic search for UDGs in eight nearby clusters. I’ll focus on the abundance of UDGs as a function of halo mass, and their radial distribution in the clusters. The latter indicates that they were likely accreted by the cluster several Gyrs ago, but are still hosted by massive dark-matter haloes. I’ll discuss implications and future prospects to learn more about their formation history and properties.