Correlation between a galaxy’s stellar mass, M_*, and the stellar mass accreted from the most massive merger according to TNG50. Panel (a): Mass fraction of the hot inner stellar halo, M_{*, halo(r < 2Re)}, compared to the total stellar mass, M_*, as a function of M_*. The solid line is the average, and the dashed lines are ±1σ scatter. In this mass range, the hot inner stellar halo mass contributes only ∼5%−30% of the total stellar mass. Panel (b): Similar to the right panel of Fig. 5, but using the total stellar mass, M_*, instead of the hot inner stellar halo mass along the x axis. Compared to Fig. 5, the correlation becomes weaker with ℛ = 0.75 and the 1σ scatter is about 0.1 dex larger in general. The ex situ fraction does not increase as gradually with increasing x as in Fig. 5, and the correlation of M_* with f_ExSitu is also weaker than M_{*, halo(r < 2Re)}.