Selected stellar particles in the tidal tails and their 3D velocities (in colour) from the M31 merger models at −1 Gyr. The M31 is fixed at (0, 0, 0), and the MW at 0 Gyr is on the z-axis. The position of the MW (in red dot) is calculated for a radial approach between the two galaxies taken as the point mass for the MW mass of model B and the M31 mass from Hammer et al. (2025). The x-marks denote the midpoint.