Growth of the IGL fraction over cosmic time in our simulated groups. The blue band represents the interquartile range of the temporal variation in the distribution of log(f_IGL) in the last ∼10 Ga of the runs, with the central solid line indicating the evolution of the median value. The vertical solid and dashed lines mark, respectively, the Q₂, and Q₁ and Q₃ quartiles of the distribution of turnaround times, when the groups reach their largest non-expanding scale around the centre of gravity.