Growth of BH mass due to mergers or accretion of the same BHs as plotted in Fig. 2: the six most massive BHs (top row) and six IMBHs (bottom row) from our standard simulation BHs5e0.1v5. Left column: merger-driven mass-growth regime. Right column: accretion-driven mass-growth regime; the two regimes are distinguished with a limiting Eddington accretion ratio = 0.1, as described in Sect. 3.2.