The High-Latitude Time-Domain Survey (HLTDS) for Roman will discover thousands of high redshift Type Ia supernovae (SNeIa) to make generation-defining cosmological constraints on dark energy and its potential time-evolution. To construct the Roman SN Hubble diagram, a strategy to obtain redshifts must be determined. While the nominal HLTDS will use only the Roman prism, in this talk I will discuss the utility of the Roman grism observations from overlap with the High-Latitude Wide-Area Survey for SNIa cosmology. We determine a galaxy grism redshift recovery rate by simulating dispersed grism images, measuring redshifts with the Grizli software and applying the measured efficiency to HLTDS catalog-level SN simulations, providing a first estimate of the total number of spectroscopic redshifts expected for Roman SN cosmology. These simulations further allow us to evaluate the size of potential systematics related to modeling the grism redshift efficiency by considering the impact of additional dependencies on stellar mass and host galaxy color.

4-4:30 PM EDT/1-1:30 PM PDT

Connect here: https://teams.microsoft.com/meet/24828383463357?p=khMZ6WS1UNGkQobLEK.