Root mean square of the relative velocity dispersion, $\sqrt{⟨v^2⟩}$, with respect to the CenA/M83 system’s barycentre, shown as a function of the mass ratio ${\overline{m}}_{\mathrm{CenA}}=m_{\mathrm{CenA}}/m_{\mathrm{Tot}}$. Velocities are measured in the Local Group frame under the minor-infall (blue) and major-infall (red) models. Dotted lines: Raw results of $\sqrt{⟨v^2⟩}$ as a function of $\overline{m}\mathrm{CenA}$, mostly lying slightly below the smoothed (solid) curves, except for a local spike near ${\overline{m}}_{\mathrm{CenA}}\approx 0.85$ in the minor infall case. This spike is interpreted as a numerical bias arising from the clustering of galaxies near the CenA/M83 barycentre position (Müller et al. 2021, 2025). The vertical dashed lines show positions of the minima in $\sqrt{⟨v^2⟩}$ for each model, indicating the best-fitting mass ratio. To avoid confusion, these vertical lines are plotted with a distinct dashed style, different from the dotted raw data lines.