Turning Galaxy Rotation Curves into Radial Cosmic Chronometers: A Nexus Paradigm Approach

We present a method for transforming galaxy rotation curves into radially resolved dynamical chronometers, enabling reconstruction of galaxy assembly histories directly from kinematic data. Within the Nexus Paradigm, the baryonic Tully-Fisher relation provides an estimate of the dynamical mass profile M dyn(r)=v 4/Ga 0, where a 0=H 0/2 pi.By Comparing this with independently derived intrinsic baryonic mass profiles, M int(r), obtained from stellar S'ersic fits and gas surface density measurements, we construct the ratio M dyn(r)/M int(r), which maps directly to a formation redshift via 1+z form(r)=(M dyn/M int) 1/4. Inverting this relation with CDM cosmology yields a radial lookback-time profile, t lb(r), representing the time since the last dynamical reconfiguration at each radius. Applying this framework to a pilot sample of SPARC galaxies spanning high-and low-surface-brightness systems, together with the Milky Way, we recover diverse radial age structures, including flat profiles consistent with coherent disk assembly and stratified profiles indicative of inside-out growth. The method operates without dark-matter halo fitting and provides a kinematic chronometer complementary to stellar-population and chemical-evolution approaches. While the inferred ages depend on the accuracy of baryonic mass reconstruction and local applicability of the evolving baryonic Tully-Fisher relation, the results demonstrate that galaxy rotation curves encode time-resolved dynamical information. This establishes the radial dynamical chronometer as a new observable for probing galaxy evolution and testing gravitational frameworks.