(a) Heat maps of the orbital distribution in the L_z–z plane for CND gas (left) and ring gas (right). The color scale shows the particle fraction in each bin (logarithmic scale), and only bins with a fraction >1 × 10⁻⁴ are plotted. White lines trace representative particle trajectories. Red arrows indicate the direction of particle motion. The red dashed ellipse indicates the nuclear-ring region. (b) Left: face-on map of the mean hydrogen number density in the dust-lane region. Right: vertical slice along the direction marked by the red arrow in the left panel; the vertical axis measures the height above the midplane, and the white arrows indicate velocity vectors projected onto the slice. The slice averages over ±100 pc along the line of sight.