Time, t_rel, necessary for the cluster to reach the relativistic phase of its collapse for various values of its total mass, M_BH (assumed to be constant and formally denoted by its ‘initial’ value, M_BH, 0, for a more direct comparison with Fig. 8 in Kroupa et al. 2020), and initial radius, R₀. The mass of the individual stellar black holes, m_BH, and the ratio η_g = M_g/M_BH, where M_g is the mass of the gas within the cluster, are given at the top of each panel. Values of the initial radius R₀ cover the interval (0.05,0.5) pc.