The Morphology Blind Spot: An Exploratory Test of Gas/Dust Proxies as Predictors of Rotation-Curve Residual Structure in Spiral Galaxies

One-dimensional rotation-curve analyses are a standard and pragmatic tool in galactic dynamics, but they necessarily compress azimuthally structured systems into radially averaged profiles. This paper explores whether information related to galaxy morphology plausibly survives this reduction strongly enough to influence residual diagnostics. Using a conservatively matched spiral-galaxy sample with rotation curves and mid-infrared photometry, we compare a coarse dust/gas-related proxy to outer-region residual amplitude and to residual coherence quantified via the Durbin–Watson statistic. We find that the morphology proxy exhibits structured, non-random associations with both diagnostics, suggesting that azimuthal baryonic complexity may contribute to residual behavior in ways not captured by purely radial modeling. The result is interpreted as a diagnostic limitation rather than a definitive physical explanation: models judged primarily by one-dimensional residual structure may be systematically insensitive to morphology-mediated effects. No alternative gravitational mechanism is proposed.