Sources in the direction of the C1 clump. The YSOs discussed in the text and in Table E.4 are identified on images in the NIR (JHK_s colour composite image), at 4.5 μm, 8 μm, 24 μm, and 70 μm. The red contour corresponds to a column density of 1 × 10²³ cm⁻², and the green contour (superimposed on the 8 μm image) to a column density of 1.6 × 10²³ cm⁻². This latter contour follows a level that is half of the N(H₂) peak’s intensity.