Spitzer 3.6 μm image of Lupus IV. The field of view is 43′ × 54′. North is up, east to the left, and scaling is logarithmic. The locations of the background stars for which the optical depth has been measured are shown as circles (100 pixels, 60′′) radius, which is the outer radius of the annulus used to measure CS). The red circles show the stars included in the sub-sample used in this study. ¹³CO(2−1) emission is shown in steps of 1 K km s^-1 between 0 and 7 K km s^-1 as contours.