Core luminosity plotted against the core mass. For comparison, a sample of ten IR dark and IR bright cores in the Snake IRDC from Henning et al. (2010) are shown with empty circles (see Sect. 4.3 and Appendix B). The black dashed line shows the accretion luminosity with a mass accretion rate of Ṁ_acc = 10⁻⁵ M_⊙ yr⁻¹ and assuming a stellar mass of M_⋆ = 0.1 × M_core and stellar radius of R_⋆ = 5 R_⊙ (see Eq. (8)). The magenta dashed lines above and below the aforementioned line show a ± 1 dex variation of the accretion luminosity in question.