All Puffed Up: Exploring Ultra-diffuse Galaxy Origins through Galaxy Interactions

Ultra-diffuse galaxies (UDGs) are mysterious, faint galaxies that challenge our understanding of galaxy evolution. I present new observations of two UDGs, selected for their unusual shapes, which hint at interactions with nearby galaxies. Using data from the Hubble Space Telescope, I identified several globular clusters in each galaxy, a feature commonly seen in more typical dwarf galaxies. Radio observations from the Jansky Very Large Array show one of these galaxies, KUG 0203-Dw1, still has some gas, though it appears to be losing it due to its environment. The other galaxy, KDG 013, has gas nearby, but it seems to belong to other galaxies in the area. These findings suggest that both UDGs likely started out as normal dwarf galaxies but have been stretched and pulled apart by interactions with larger galaxies, making them appear more diffuse. These UDGs are part of a now completed sample of five exhibiting tidal features in the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) area (∼150 square degrees). Four of these UDGs, consistent with dwarfs ‘puffed-up’ by tidal interactions, contrast with an outlier suggesting a possible dwarf merger origin. These findings support tidal heating as a viable formation pathway for UDGs. I will also highlight other areas of dwarf galaxy research I am actively involved with.