Time evolution of M/L_V for all IMFs considered (vDC, SAL, CAN, MKDP). We assume that the system is gas free and that neither stars nor remnants are leaving (the dashed lines show the change of the M/L_V value if only certain fractions of remnants are kept). The upwards-pointing blue arrow demonstrates that if we would assume more massive remnants (e.g. due to implosion directly to a BH without a SN explosion), then this would lead to larger values of M/L_V. The models are computed for the case of M_UCD = 10⁹ M_⊙, however, results are mass independent. The only exception is the MKDP IMF, which depends on initial object mass, M_UCD, and also contains a large fraction of mass in high mass stars, and is plotted for M_UCD = (10⁹, 10⁸, 10⁷ M_⊙, bottom to top) and different fractions of remnants retained (100%, 10%, 0%). Left panel: the evolution for [Fe/H] = −2. Right panel: the evolution for [Fe/H] = 0. The grey band indicates the span of the observed present-day M/L_V values, approximately five to ten for the majority of UCDs (Mieske et al. 2008; Dabringhausen et al. 2009). The scales are identical for both panels.