Gaia CMD using M_G versus G_BP − G_RP showing the SigMA-selected Sco-Cen members. Left: SigMA cluster members that pass the photometric quality criteria as given in Eq. (D.2). Middle: Potential contamination from older sources (orange), selected with a 25 Myr isochrone from PARSEC (black line) and Baraffe et al. (2015, dashed black line) and an additional cut at M_G > 3 mag (dashed-dotted black line), which excludes the UMS. The combined conditions indicate contamination from older sources of about 6–7% when using the given photometric quality criteria and no stability cut. Right: Substellar candidates (red dots) selected with a 0.08 M_⊙ isomass line from Baraffe et al. (2015, dark red line) using only the younger source from the middle panel. This cut indicates that roughly 19% of substellar sources are within the SigMA Sco-Cen members when the mentioned cuts and photometric quality criteria are applied and extinction effects are ignored. More details on the quality criteria, the selection borders, and the isochrone models are given in Appendix D.