Accreted mass fraction vs. total stellar mass for ETGs. Our VEGAS measurements are given as red filled and open triangles (see text for details). Black circles correspond to other BCGs from the literature (Seigar et al. 2007; Bender et al. 2015; Iodice et al. 2016) and the magenta dot represents NGC 1316 (Iodice et al., in prep.). Red and blue regions indicate the predictions of cosmological galaxy formation simulations by Cooper et al. (2013, 2015) and Rodriguez-Gomez et al. (2016), respectively. Purple-grey points show the mass fraction associated with the streams from Table 1 in Cooper et al. (2015) for comparison to the observations shown by open symbols.