TUNER model fits to the observed data (black circles) for the dust and CO line SEDs. The 50th percentile is shown by a dotted black line and the 16–84th percentile range as a shaded grey region. The representative density contributions to the observed dust (left) and CO line (right) SED from each molecular gas density bin of log(n(H₂)) [cm⁻³] = 1 (dark blue), 2 (blue), 3 (light blue), 4 (light orange), 5 (orange), and 6 (red) are shown in solid coloured curves.