Column density profiles for a horizontal cut through the maps Figs. 8−9. Shown are the true column density (solid black line; uppermost lines, convolved to 18.3″ resolution), the estimate derived from 18.3″ data at all wavelengths (black dotted line), Method A (blue solid line), and Method B (red solid line). The lower frames correspond to the case with an internal heating source. The noise is 0.3 times (frames a and c) or 3.0 times (frames b and d) times the default value.