Universal Gravitational Response from SPARC Rotation Curves: Baseline Parameters, Tension Subsets, and an Environment Consistency Test

This record provides the current preprint (v3) of “Universal Gravitational Response from SPARC Rotation Curves: Baseline Parameters, Tension Subsets, and an Environment Consistency Test.” We perform a global fit of a universal Yukawa-type gravitational response function to a quality-selected SPARC sample, profiling stellar mass-to-light ratios per galaxy while fitting two global parameters (\beta_0, m_\chi). We deliberately test the strict null hypothesis that a single, unscreened radial response with constant (\beta_0, m_\chi) can describe the SPARC population. Under this strict null, we identify a tension subset whose fitted mass-to-light ratios saturate prior bounds and which dominates the total misfit, indicating that additional structure (e.g., environment dependence, mass-dependent running, screening, or improved treatment of observational systematics) may be required. Environmental information is not used in the rotation-curve fit; instead, we report an a posteriori consistency test using an internal residual-based proxy against an independent external environment proxy.