Towards Understanding the Origin and Evolution of Ultra-Diffuse Galaxies

Recent observations of Ultra-Diffuse Galaxies (UDGs, which have the luminosities of dwarfs but sizes of giant galaxies) have picked up a lot of attention by the community. They are routinely found in clusters, while one would naively expect them to be easily disrupted by tidal interactions in such over-dense environments. Indeed, current theoretical models can produce UDGs as efficiently in the field. However, observational constraints on whether the formation of UDGs is -somehow- affected by cluster and group environments are currently lacking. I will summarise recent developments that address this question, results which are based on the synergy between the GAMA@AAO and KiDS@ESO surveys. Surprisingly, these show that clusters indeed host a surprisingly high relative number of UDGs compared to lower-density environments. I will discuss implications and future prospects (especially regarding measurements of their total masses) to learn more about the properties and formation histories of these elusive galaxies.