Characterizing SMUDGes UDGs with Deep Atomic Gas Observations

We present deep neutral hydrogen (HI) follow-up observations of ultra-diffuse galaxies (UDGs) in the Coma Cluster and Stripe82 regions as part of the Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes) survey. With the ever-growing number of UDG detections and evidence for diversity within this population, multiple formation mechanisms have been proposed: their large sizes and diffuse stellar distributions may be a result of star formation feedback, or they may have formed in dwarf halos with higher than average angular momenta. Large samples of bonafide UDGs are required to investigate these mechanisms, which requires distance information for photometric candidates, particularly in the field. However, optical redshifts can be very expensive to obtain for such faint objects. An alternative is to exploit the HI reservoirs of gas-rich UDG candidates; their utility extends beyond obtaining redshifts, as both of the aforementioned formation mechanisms provide clear predictions for field UDG gas reservoirs that can be constrained via HI observations. Our HI follow-up sample covers a range of environments, from the dense Coma Cluster center out to beyond 10 cluster virial radii. Using the results from our completed pilot survey as well as more recent observations, we will compare the properties of UDGs across these environments and constrain different formation mechanisms.