Testing Lens Models of PLCK G165.7+67.0 Using Lensed SN H0pe (2510.07637v1)

Abstract: Supernova H0pe is a multiply-imaged Type Ia supernova (SN Ia) and the second lensed SN to yield a measurement of the Hubble constant by the time-delay cosmography method, finding $H_0 = 75.4^{+8.1}_{-5.5} \text{km s}^{-1} \text{Mpc}^{-1}$. We investigate the seven lens modeling approaches used to derive $H_0$, assessing their agreement with $\Lambda \text{CDM}$ constraints from SN Ia surveys through a purely observational comparison. While photometrically derived magnifications yield distance moduli in line with $\Lambda \text{CDM}$ expectations, our comparison reveals that lens model predictions, even the most precise ones, consistently overestimate the magnification, with a offset of $ \Delta \mu > 1$ mag. This known bias, already appreciated by modeling teams, is independently confirmed through our analysis and highlights the value of lensed SNe as a tool to test model accuracy. If unaccounted for, such magnification biases can propagate into uncertainties in derived cosmological parameters, including $H_0$, and affect the interpretation of future precision measurements. These findings highlight a critical challenge for precision cosmology using strongly lensed transients. With next-generation surveys such as LSST, Roman, and Euclid poised to discover many more gravitationally lensed supernovae, the development and validation of robust, accurate lens models will be essential for using these rare events to probe cosmology.