Program: GS-2021B-Q-243

Type Ia Supernovae (SN Ia) are precise cosmological distance indicators after correcting for their light-curve shape and color. However, even after those corrections, their Hubble residuals correlate with large-scale host-galaxy properties such as host mass and nuclear metallicity. Currently, the most precise cosmological analyses make an empirical correction based on the host mass, applying the same correction for all SNe from galaxies with the same mass regardless of redshift. This can introduce a systematic bias that is larger if the host galaxy demographics evolve significantly with redshift --- this is currently the case since the current low-z sample was compiled from SN searches that targeted massive galaxies while high-z surveys were untargeted. New surveys such as the Foundation and Swope SN surveys draw their samples from untargeted surveys, matching the high-z strategy and reducing potential bias. But this hinges on obtaining host-galaxy redshifts for the lowest-luminosity galaxies, without which the sample is still biased to high-mass galaxies. We propose obtaining redshifts of the faintest galaxies in the Foundation and Swope samples to include these objects in the final cosmological analysis and mitigate this potential bias. Furthermore, we will obtain spectroscopic measurements of star-formation rate and metallicity, which may unravel the underlying cause of the empirical host-galaxy correction.