a) (J − K_s,K_s) color–magnitude diagram. b) (H − K_s, J − H) color–color diagram. All detections in the SOFI-field of view (Fig. 1, bottom right) are included, except for those with an error larger than 0.1 mag in any of the color indices. Blue symbols indicate OB stars (see Sect. 4.1); red (Class 0/I) and green (Class II) symbols indicate Lada classified sources (see Sect. 3.2). The solid line is the zero-age main sequence (ZAMS, Blum et al. 2000; Bessell & Brett 1988) at a distance of 0.7 kpc. The dashed line indicates the separation between the cluster and the foreground population, which is indicated with cyan symbols. The dotted line is the extinction vector (Cardelli et al. 1989) and the dot-dashed line is the cTTS locus (Meyer et al. 1997).