Are massive dense clumps truly sub-virial? A new analysis using Gould
  Belt ammonia data
  Dynamical studies of dense structures within molecular clouds often conclude
that the most massive clumps contain too little kinetic energy for virial
equilibrium, unless they are magnetized to an unexpected degree. This raises
questions about how such a state might arise, and how it might persist long
enough to represent the population of massive clumps. In an effort to
re-examine the origins of this conclusion, we use ammonia line data from the
Green Bank Ammonia Survey and Planck-calibrated dust emission data from
Herschel to estimate the masses and kinetic and gravitational energies for
dense clumps in the Gould Belt clouds. We show that several types of systematic
error can enhance the appearance of low kinetic-to-gravitational energy ratios:
insufficient removal of foreground and background material; ignoring the
kinetic energy associated with velocity differences across a resolved cloud;
and over-correcting for stratification when evaluating the gravitational
energy. Using an analysis designed to avoid these errors, we find that the most
massive Gould Belt clumps harbor virial motions, rather than sub-virial ones.
As a byproduct, we present a catalog of masses, energies, and virial energy
ratios for 85 Gould Belt clumps.
