Contour map of the surface density of NIR sources from the SofI data, overlaid with the K_s image of Pismis 24 and G353.2+0.9. Contours range from 240 stars arcmin^-2 (the average for field stars plus 2σ, using the values found in the southern field) in steps of 30 stars arcmin^-2 (~1σ). Also overlaid: (dashed contour) the surface density of IRAC sources (level 36 stars arcmin^-2 of Fig. 5) delineating Pis24 core; (open circles) the location of sources with a NIR excess (see the text for the selection criteria). All data used in figure have K_s< 16 and photometric errors <0.3 mag both in K_s (surface density) and in all JHK_s bands (NIR excess).