Description
Type Ia supernovae (SNe Ia) have played an important role in both astrophysical and cosmological analyses. Traditionally, these analyses rely on precise spectroscopic measurements of either the supernova or its host galaxy. The Vera C. Rubin Observatory Legacy Survey of Space and Time is expected to begin operations in early 2026, and will discover and measure millions of SNe Ia. However, spectroscopy will be feasible for only a small fraction. To fully exploit the number of detected SNe Ia, the development of photometric analyses is required. In this work, we present a photometric approach to SN Ia science, using a sample of ~3,500 SNe Ia discovered by the Dark Energy Survey (DES). We estimate photometric redshifts from the SN light curves, using flexible priors on the light curves of the SNe. Our photometric redshift estimator produces a low ~3% catastrophic outlier rate and results in a sample of usable SNe Ia that is almost double the size of the DES sample with host spectroscopic redshifts. Furthermore, our approach enables studies of lower-mass host galaxies, a regime often underrepresented in spectroscopic surveys due to their faint apparent magnitudes. We present the first results of our photometric analysis and explore its astrophysical and cosmological implications.
