Main panel: Stellar mass (black), accreted mass (red), outer stellar-halo mass (blue) and in-situ mass in the stellar halo (green) as a function of virial mass for the 5131 isolated galaxies (dots) in our sample. Solid lines and shaded regions show the median trend and the 25th-75th percentile regions. The dashed magenta line shows the Moster et al. (2018) abundance-matching relation at z = 0, whereas the solid orange line shows the accreted mass obtained when using publicly available values from a sub-halo membership method, based on SUBFIND. The two black segments at the top indicate the range of mass of the stacks shown in Fig. 4. The middle panel shows the accreted-to-total stellar-mass fraction, f_acc = M_acc/M_*, as a function of virial mass, and the bottom panel, f_acc, as a function of galaxy stellar mass. The incompleteness of the sample at stellar masses of M_* < 10⁸ M_⊙ generates a spurious upturn in the trend. With a pink line, we show the results reported by Rodriguez-Gomez et al. (2016) for the Illustris simulation.