Holographic Residual Dark Matter II: Galaxy-Scale Phenomenology and Extended Flat Circular Velocities

This technical preprint presents Paper II of the Holographic Residual Dark Matter framework. Paper I introduced the core CDM-like effective component. The present note focuses on the galaxy-scale phenomenology of the residual gravitational response X. In the model, the galaxy-scale residual acceleration is taken to have the MOND-like form a_X = sqrt(a_b a_H), where a_b is the baryonic Newtonian acceleration and a_H is a holographic residual acceleration scale of order c H_0 / 2 pi. For an isolated galaxy with approximately fixed enclosed baryonic mass M_b at large radius, this gives a_X proportional to 1/r and directly yields v_f^4 = G M_b a_H, corresponding to the baryonic Tully-Fisher relation. The same scaling naturally permits extended flat circular velocities at large radii, with the eventual cutoff controlled by environment, external-field effects, boundary-memory effects, or projection-scale limitations rather than a sharp particle-halo edge. The work is presented as a phenomenological galaxy-scale consequence of the HRDM framework. It does not claim a full microscopic derivation of the residual acceleration law; rather, it identifies the mathematical consequences and observational tests of the proposed galaxy-scale response. Merging-cluster lensing/gas offsets are reserved for a subsequent note.