Infrared colour–magnitude diagram (left) and colour–colour diagram (right) for the stellar content of our survey, with spectral type of the stars coded with colour. In the left panel the solid, dashed, and dotted lines show the ZAMS location from Siess et al. (2000) at a distance of 50, 100, and 300 pc respectively. Giant candidates, are over-plotted with a star-symbol. Pre-main sequence stars are shown with squares. We include the reddening vector for an extinction of A_V = 5 mag. In the right panel, the thick black lines show the location of main sequence (solid) and giant (dashed) stars, the thin black dashed line and the thin black dotted lines show the location of classical T Tauri stars (TTS) and associated errors respectively. The black parallelogram shows the location of Herbig AeBe stars (see text for details).