Predictions for the Roman Space Telescope
NASA's Nancy Grace Roman Space Telescope (Roman) is scheduled to launch in May 2027. Pearson has shown that Roman can find stellar streams from thin Palomar 5-like globular clusters in external galaxies out to about 6 Mpc (Pearson et al. 2019). Recently, C. Aganaze (UCSD) showed that Roman will be able to detect gaps in such streams out to 2-3 Mpc (Aganze, Pearson et al. 2023), a volume which includes about 200, mostly dwarf, galaxies. Thin streams emerging from globular clusters have never been detected beyond the Milky Way, but they are of particular interest, since these are dynamically cold and retain a memory of past interactions for longer periods of time. Thin streams are also more sensitive to perturbations from low-mass dark substructure due to the globular cluster streams’ low intrinsic velocity dispersions. Large samples of gaps in streams in external galaxies will open up a new era of statistical analyses of gap characteristics, which can be used to constrain dark matter models.