Ellipticals and brightest cluster galaxies param.

We determine the contribution of this excess light (EL) at each radius from the difference between the surface flux profiles of BCGs and LNEs. It is small in the center but increases steeply to 50% at ~3kpc radius. The shape of these profiles suggests that BCGs could be formed from LNEs in three major merger processes.

This is also consistent with the mild increase of the Sersic indices from n~4 to n~6, as confirmed in merger simulations. We note that minor mergers cannot be the dominant origin of the BCG's EL because they deposit too few stars at intermediate radii r<~20kpc. The shape of the EL profile also explains a detected offset of 0.14dex of the fundamental planes for BCGs and LNEs relative to each other.