Molecular clumps disguising their star formation efficiency per freefall
  time: What we can do not to be fooled
  The presence of a volume density gradient in molecular clumps allow them to
raise their star formation rate compared to what they would experience were
their gas uniform in density. This higher star formation rate yields in turn a
higher value for the star formation efficiency per freefall time that we
measure. The measured star formation efficiency per freefall time
$\epsilon_{\rm ff, meas}$ of clumps is therefore plagued by a degeneracy, as
two factors contribute to it: one is the density gradient of the clump gas, the
other is the intrinsic star formation efficiency per freefall time
$\epsilon_{\rm ff, int}$ with which the clump would form stars should there be
no gas density gradient. This paper presents a method allowing one to recover
the intrinsic efficiency of a centrally-concentrated clump. It hinges on the
relation between the surface densities in stars and gas measured locally from
clump center to clump edge. Knowledge of the initial density profile of the
clump gas is not required. A step-by-step description of the method is provided
as a tool in hand for observers. Once $\epsilon_{\rm ff, int}$ has been
estimated, it can be compared with its measured, clump-averaged, counterpart
$\epsilon_{\rm ff, meas}$ to quantify the impact that the initial gas density
profile of a clump has had on its star formation history.
