A Bulge Escape-Based Interpretation of Galactic Rotation Velocity Without Dark Matter: Formation of the Galactic Disk and Velocity Equalization

Galactic rotation curves have long been observed to exhibit a nearly constant rotational velocity at large radii, in contrast to the prediction of simple gravitational models, which suggest that orbital velocity should decrease with increasing distance from the galactic center. This discrepancy has been consistently confirmed through observations, and one of the most widely adopted interpretations is the dark matter model, which assumes the presence of an additional, non-luminous mass component that provides the necessary gravitational force in the outer regions of galaxies. However, when the formation and evolution of galaxies are considered as time-dependent dynamical processes, it is possible that such velocity structures may arise without requiring additional mass components. In this study, we propose an integrated dynamical mechanism that can simultaneously account for both the flattening of galactic rotation curves and the high stellar density observed in the inner regions of galactic disks. We assume that early galaxies were dominated by highly dense bulge structures, from which stars gradually escaped over extended timescales. In the early stages, when the bulge mass is large, only stars with sufficiently high velocities can escape. As time progresses, continuous stellar escape leads to a reduction in the central mass, resulting in a gradual weakening of the bulge gravitational potential and a corresponding decrease in the escape threshold. At the same time, the stellar disk formed by previously escaped stars evolves into a collective gravitational structure that actively influences subsequent dynamical processes. In this framework, the disk is not merely a passive outcome of stellar redistribution, but a dynamically active system whose collective gravity can affect the escape of stars from the bulge. Specifically, as the bulge gravitational potential weakens, the collective gravity of the disk may act to lower the effective escape barrier, thereby facilitating further stellar escape. This interaction can enhance the rate of stellar outflow from the bulge, leading to an increased flux of stars migrating into the disk. As a result, a large number of stars are supplied to the disk region, particularly toward its inner parts, producing a relatively high stellar density. In this interpretation, the enhanced inner density is not simply the result of gravitational concentration, but rather a consequence of increased stellar inflow driven by the coupled interaction between the weakening bulge potential and the gravitational influence of the disk. In parallel, this escape process also affects the velocity distribution of stars. While early escaping stars initially possess relatively high velocities, the progressive decrease in escape velocity, combined with long-term changes in the gravitational environment, leads to a gradual convergence of stellar velocities over time. In this study, this phenomenon is defined as a process of velocity convergence, in which initially diverse stellar velocities evolve toward similar values. When sufficiently developed, this process may naturally produce a rotation curve that remains approximately constant across a wide range of galactic radii. Importantly, both the velocity convergence and the formation of the density structure described in this study are not directly governed by bulge rotation or a single coherent rotational framework. Instead, they emerge from the coupled effects of bulge mass reduction, disk gravitational influence, and long-term dynamical evolution involving stellar escape and redistribution. Therefore, this study suggests that both the flattening of galactic rotation curves and the inner density enhancement of galactic disks may be understood within a unified dynamical framework that incorporates the active gravitational role of the disk. This perspective provides a conceptual alternative to purely static mass-based interpretations and offers a basis for further investigation through observational and dynamical studies.