Abstract The tight empirical correlation linking the stellar disk scale length Rd to the dark matter scale radius r0 has been proposed as potential evidence for a fundamental coupling between baryons and dark matter beyond gravity. We re-examine the physical origin of this relation using a sample of 31 galaxies drawn from the NIHAO cosmological hydrodynamical simulations, which include no dark matter–baryon interactions other than gravity and baryonic feedback processes. NIHAO naturally reproduces both the normalization and the small scatter of the observed Rd − r0 relation at z = 0, while showing a slightly shallower distribution. By tracking galaxies from z = 2 to z = 0, we identify three evolutionary classes: systems undergoing disk expansion, contraction, and quasi-static galaxies. Using a Bayesian hierarchical framework, we provide the first evolutionary characterization of the Rd − r0 relation, tracing how its normalization, slope, and intrinsic scatter evolve across cosmic time, from z = 2 to the present-day Universe. Together with a mild decrease in normalization (by ~0.07 dex) and a flattening of the slope from α ≃ 1.05 to α ≃ 0.95, we find that the intrinsic scatter weakly decreases toward lower redshift, indicating that galaxies tend to evolve along the relation, jointly re-balancing their stellar and dark matter scales. Comparing hydro simulations with their dark matter only counterparts, we can isolate the effect of baryons and baryonic feedback on dark matter evolution. Our results indicate that stellar feedback alone can reshape the central potential and naturally establish the observed coupling between luminous and dark matter, without the need to invoke modifications to the dark sector.
Alrawas et al. (Fri,) studied this question.