Type Ia Supernova Cosmology with Photometric Redshifts

Cosmological analyses with Type Ia Supernovae (SNe Ia) have traditionally been reliant on spectroscopy for both classifying the type of supernova and obtaining reliable redshifts to measure the distance-redshift relation. While obtaining a host galaxy spectroscopic redshift for most SNe is feasible for our current datasets, it will be physically impossible for upcoming surveys such as the Vera Rubin Legacy Survey of Space and Time (LSST), which will observe on the order of millions of SNe. We present work in the context of the Dark Energy Survey (DES) to address this problem by utilizing photometric redshifts inferred from the SN light-curve in combination with host galaxy photometric redshift estimates to measure cosmological parameters with Type Ia Supernovae. In particular, we consider the well-characterized Self-Organizing Map redshifts (SOMPZ) used in the DES weak lensing analyses applied to the DES 5-year photometrically-classified SN sample. We present preliminary results to evaluate cosmological biases and validate our analysis using detailed catalog-level simulations. This work lays the foundation for fully photometric SNe Ia cosmological analyses to be done without the limitations of spectroscopy.