Angular-Velocity Offsets in Galactic Rotation Curves

Understanding the distributions of dark-matter halos in galaxies is crucial for testing ΛCDM in small scales. In this talk I will present a phenomenological pattern, found in the rotational data of disk galaxies, which may point to an underlying property of dark-halo distributions. The pattern is revealed by re-expressing rotation curves in terms of angular velocities. We find that in a large sample of 143 high-quality rotation curves, the difference between observed and baryon-predicted angular velocities is well-described by a constant shift. This constant angular-velocity offset provides a surprisingly effective fit, outperforming traditional dark-halo models and Modified Newtonian Dynamics (MOND). Incorporating the constant-offset feature into the dynamical equations yields a new, single-parameter dark-halo profile. The new profile is explicitly and intrinsically linked to the baryonic distribution. Our findings may point toward a universal regularity in disk galaxies' rotation, with implications for both dark matter phenomenology and alternative theories of gravity.