Left: column density map of G28.53-0.25, obtained from SED fit to Herschel 160, 250, 350, 500 μm data. Black contours indicate the levels N_dust = 2.5,3,4,6 × 10²² cm^-2, white-dashed contour outlines the approximate completeness level, and ellipse is taken from Simon et al. (2006b), defining the IRDC. Right: line integrated ¹³CO 1 → 0 emission in colour scale (in [K km s^-1]) between v = 82 and 90 km s^-1, the velocity range of the bulk emission of G28.53-0.25, and the associated GMC. The Herschel H₂ column density is overlaid as black contours (levels 2,2.5,3,4,6 × 10²² cm^-2) and the IRDC is outlined by an ellipse (Simon et al. 2006b).