Fraction of the filament mass derived from ¹³CO emission dependent on the box-diameter of the mask separated by distances. Top left panel: d < 2 kpc, top right panel: 2 kpc < d < 4 kpc, bottom left panel: 4 kpc < d < 8 kpc, bottom right panel: d > 8 kpc. One curve describes one fully correlated filament at its distance estimate. The gray lines indicate the physical beamsize at distances of 2, 3, 6, and 8 kpc. The black lines show the integrated theoretical radial profiles, which describe a Plummer-like distribution p = 1.5 (dashed) or p = 2.0 (dash-dotted), and a Gaussian distribution with a dispersion of w = 1.0 (dotted).