Extinction map toward W3 Main. The image shows the negative K_s-band image with logarithmic stretch. Overplotted in dashed black contours is the extinction map derived from the H − K_s colors of the stars using the extinction law of Nishiyama et al. (2009). Contours at A_Ks = 2, 2.5, 3.0 and 3.5 mag are shown. The red contours display 450 μm continuum emission observed by SCUBA (Ladd et al. 1993; Di Francesco et al. 2008), highlighting the location of the dense and cold dust. The contours of 10%, 20%, 40% and 80% of the maximum flux value (6.4 Jy/beam) are shown. The dust emission peaks around IRS5 and IRS4.