Type Ia Supernova Environmental Correlations Trace Local Gravitational Potential

Standardized Type Ia supernova (SN Ia) brightnesses exhibit persistent correlations with host galaxy properties. The most prominent—the “mass step”—is typically treated as an empirical nuisance parameter. Additional correlations have been reported with galactocentric position and local dark matter density. A meta-analysis combining published results from the Dark Energy Survey 5-Year sample (1533 SNe) and the Open Supernova Catalog (222 SNe) shows that these apparently distinct effects trace a single underlying variable: local gravitational potential. Hubble residuals correlate with estimated gravitational potential at 5.2σ significance, with supernovae in deeper potentials appearing systematically brighter after standardization.