The width of Herschel filaments varies with distance
  Context: Filamentary structures in nearby molecular clouds have been found to
exhibit a characteristic width of 0.1 pc, as observed in dust emission.
Understanding the origin of this universal width has become a topic of central
importance in the study of molecular cloud structure and the early stages of
star formation. Aims: We investigate how the recovered widths of filaments
depend on the distance from the observer, by using previously published results
from the Herschel Gould Belt Survey. Methods: We obtained updated estimates on
the distances to nearby molecular clouds observed with Herschel by using recent
results based on 3D dust extinction mapping and Gaia. We examined the widths of
filaments from individual clouds separately, as opposed to treating them as a
single population. We used these per-cloud filament widths to search for signs
of variation amongst the clouds of the previously published study. Results: We
find a significant dependence of the mean per-cloud filament width with
distance. The distribution of mean filament widths for nearby clouds is
incompatible with that of farther away clouds. The mean per-cloud widths scale
with distance approximately as 4--5 times the beam size. We examine the effects
of resolution by performing a convergence study of a filament profile in the
Herschel image of the Taurus Molecular Cloud. We find that resolution can
severely affect the shapes of radial profiles over the observed range of
distances. Conclusions: We conclude that the data are inconsistent with 0.1 pc
being the universal characteristic width of filaments.
