Baryonic Deficits in SPARC Rotation Curves: Density- and Acceleration-Conditioned Trends in the Full Late-Type Sample

We examine baryonic contributions to galaxy rotation curves using mass-model files from the SPARC database compiled by Federico Lelli, Stacy S. McGaugh and James M. Schombert (2016). Using a fixed and reproducible parsing protocol applied to publicly available rotmod files, we compute baryonic fractions R (r) = (v_"bar" (r) ) / (V_"obs" (r) ) and a derived deficit statistic (r) = (1 - R, 0) for 165 late-type galaxies with at least six valid radial points. Galaxy-level summaries include the number of radial points, the median baryonic fraction, the mean deficit, the rms dispersion of deficits, and an effective disk surface-density proxy defined as the median disk surface brightness across radii. The sample exhibits a broad distribution of baryonic fractions with global mean medianR = 0. 602 ± 0. 015 (standard error of the sample mean; σ ≈ 0. 194). Deficits decrease systematically with increasing baryonic acceleration, reproducing the radial acceleration relation previously reported in SPARC analyses. When galaxies are grouped by effective surface density, higher-density systems exhibit systematically larger baryonic fractions and lower deficits. Stratifying radial points by surface-density tertiles reveals modest offsets in the deficit–acceleration relation at fixed baryonic acceleration, with lower-density galaxies exhibiting larger residual deficits. These results provide a reproducible empirical characterization of baryonic deficits across the SPARC rotation-curve sample and suggest that effective baryonic surface density organizes part of the residual variation beyond acceleration scaling. The analysis notebook and derived statistics are available at: https: //doi. org/10. 5281/zenodo. 18904974