Coupling between stellar and dark matter components from major and minor mergers. A: major mergers. The left panels show all the TNG ETGs, color coded by their fraction of stellar mass accreted by major mergers. On the right we consider only galaxies with at least 30% of their stellar mass accreted from major mergers and color code them according to the fraction of recently produced in-situ stars Δ_{insitu, z ≤ 1}. Major mergers cause the coupling between stellar and dark matter components, especially in galaxies that have not recently accreted cold gas. B: minor mergers. Here we consider galaxies with stellar mass fraction accreted from major mergers in the narrow range 0.1 < ΔM_*, major/M_* < 0.2. In the left panels, galaxies are color coded by the fraction of stellar mass accreted from minor mergers ΔM_*, minor/M_* and on the right by the fraction of recently produced in-situ stars Δ_{insitu, z ≤ 1}. Dry minor mergers also help to set up the similarity between stellar and dark matter halo structure.