Scaling relation between the total stellar mass of galaxy groups and their halo masses from our baseline model. The grey line shows the best-fit results, with the shaded regions illustrating the corresponding 68% and 95% credible intervals. The parameter values are provided in Table 3. The black points represent the halo masses calculated by allowing A_s to vary for each stacked bin while fixing other parameters to their best-fit values from the joint fit. The error bars correspond to the 68% credible intervals of the new constrained A_s distributions. The corresponding ${\mu }_{log{M}_{\star }^{\mathrm{grp}}}$ values for these points are the mean log-stellar mass of all groups in the given stacked bin. Predictions from simulations, represented by dashed lines, are estimated from the mock catalogue built in Sect. 3. All values of ${\mu }_{log{M}_{\star }^{\mathrm{grp}}}$ are converted to a h₇₀ cosmology for comparison, with $M_{\star }^{\mathrm{grp}}$ from simulations scaled as $h_{70}^{-1}$ and those from observations scaled as $h_{70}^{-2}$. We note that the scaling relation is demonstrated as the mean log-stellar mass at a fixed halo mass.