Bottom panel: mass growth of a MBH in a galaxy that becomes a large spheroid by z = 0. The evolution is extracted from a merger tree describing a dark matter halo of mass at z = 0. The galaxy is the central galaxy in a group-sized halo. Middle panel: evolution of the Eddington rate vs. redshift. Top panel: evolution of the spin parameter. After an early phase of rapid accretion and growth, the accretion rate declines and the MBH is fed by stellar winds only (quiescent phase) over the past 6 Gyr. Today's spin is defined by a MBH–MBH merger, with a mass ratio q = 0.35 that occurred ~3 Gyr ago. Here, the spins of the MBH before MBH–MBH coalescence are shown as blue empty circles and the spins after coalescence are shown as red filled dots.