A Simple Perspective on the Mass-Area Relationship in Molecular Clouds
  Despite over 30 years of study, the mass-area relationship within and among
clouds is still poorly understood both observationally and theoretically.
Modern extinction datasets should have sufficient resolution and dynamic range
to characterize this relationship for nearby molecular clouds, although recent
papers using extinction data seem to yield different interpretations regarding
the nature and universality of this aspect of cloud structure. In this paper we
try to unify these various results and interpretations by accounting for the
different ways cloud properties are measured and analyzed. We interpret the
mass-area relationship in terms of the column density distribution function and
its possible variation within and among clouds. We quantitatively characterize
regional variations in the column density PDF. We show that structures both
within and among clouds possess the same degree of "universality", in that
their PDF means do not systematically scale with structure size. Because of
this, mass scales linearly with area.
