A New Diagnostic for MOND Fits in SPARC Galaxies: TheVbar/Vflat Ratio

We present a systematic chi-squared analysis of the full SPARC sample of 175 late-type galaxies (3, 391 rotation curve data points), comparing four physically motivated models: MOND and threedark matter halo profiles (NFW, Isothermal, Burkert). Using chi-squared per degree of freedom (chi2ᵣed) and the corrected Akaike Information Criterion (AICc) as primary statistics, we find: (A) Cored isothermal profiles are preferred over cuspy NFW in 100 vs. 15 galaxies by decisive AICc (|ΔAICc|>2) ; Wilcoxon p = 9. 3×10 ¹⁹. (B) MOND achieves chi2ᵣed < 2. 0 in 28. 6% (50/175) of ⁻galaxies; median R² = 0. 732. (C) We introduce Vbar/Vflat as a novel model-free MOND diagnostic: logistic regression predicts MOND fit quality with 71. 4% accuracy (AUC = 0. 649; 10-fold CV0. 714±0. 008; threshold 0. 194). (D) The Radial Acceleration Relation is confirmed: Pearson r = 0. 9576, σ = 0. 163 dex, N = 3, 391. (E) BTFR slope from stellar population synthesis masses = 3. 813 ± 0. 084, 2. 2σ from MOND (4. 0). Comparison against EAGLE, IllustrisTNG, SIMBA, and FIRE-2 indicatestension with standard ΛCDM, subject to the caveat that this comparison is not selection-functionmatched. All results derive from published SPARC data without modification.