A possible observational bias in the estimation of the virial parameter
  in virialized clumps
  The dynamics of massive clumps, the environment where massive stars
originate, is still unclear. Many theories predict that these regions are in a
state of near-virial equilibrium, or near energy equi-partition, while others
predict that clumps are in a sub-virial state. Observationally, the majority of
the massive clumps are in a sub-virial state with a clear anti-correlation
between the virial parameter $\alpha_{vir}$ and the mass of the clumps $M_{c}$,
which suggests that the more massive objects are also the more gravitationally
bound. Although this trend is observed at all scales, from massive clouds down
to star-forming cores, theories do not predict it. In this work we show how,
starting from virialized clumps, an observational bias is introduced in the
specific case where the kinetic and the gravitational energies are estimated in
different volumes within clumps and how it can contribute to the spurious
$\alpha_{vir}-M_{c}$ anti-correlation in these data. As a result, the observed
effective virial parameter $\tilde{\alpha}_{eff}<\alpha_{vir}$, and in some
circumstances it might not be representative of the virial state of the
observed clumps.
