Ultra-Deep Field Surveys with the Nancy Grace Roman Space Telescope

The Nancy Grace Roman Space Telescope (“Roman” hereafter), planned for launch later this decade, offers Hubble-quality imaging over a field of view about two orders of magnitude beyond that of HST or JWST. This dramatically opens up completely new areas of parameter space for extragalactic deep field science, including cosmology, supernovae, and the evolution of stars, galaxies and supermassive black holes. The Wide Field Instrument (WFI) on Roman has an instantaneous field of view of ~1000 square arcminutes, with higher sensitivity than HST over wavelengths from the optical to the near-IR. This would enable Ultra Deep Field (UDF)-like depths at or beyond those previously obtained, reaching to 30th magnitude or beyond, over an area about 100-200x larger, providing valuable synergies with a variety of HST and JWST surveys of the distant universe. Moreover, wider Roman surveys, on scales of tens to hundreds of square degrees or more, would readily achieve depths comparable to large surveys with HST and JWST, and would also enable multi-epoch supernova science that could be matched in area to the Rubin Deep Drilling fields, Euclid deep fields, or other large survey areas. Finally, achieving UDF-quality imaging over areas 100-200x larger than the current UDF surveys would vastly increase the sample sizes of galaxies in the epoch of reionization, dramatically increasing the discovery potential of these rare populations of galaxies at these earliest epochs of cosmic time.