Thermal balance and comparison of gas and dust properties of dense
  clumps in the Hi-GAL survey
  We present a comparative study of physical properties derived from gas and
dust emission in a sample of 1068 dense Galactic clumps. The sources are
selected from the crossmatch of the Hi-GAL survey with 16 catalogues of NH$_3$
line emission in its lowest inversion (1,1) and (2,2) transitions. The sample
covers a large range in masses and bolometric luminosities, with surface
densities above $\Sigma=0.1$ g cm$^{-2}$ and with low virial parameters
$\alpha<1$. The comparison between dust and gas properties shows an overall
agreement between $T_{\textit{kin}}$ and $T_{\textit{dust}}$ at volumetric
densities $n\gtrsim1.2\times10^{4}$ cm$^{-3}$, and a median fractional
abundance $\chi$(NH$_3$)$=1.46\times10^{-8}$. While the protostellar clumps in
the sample have small differences between $T_{\textit{kin}}$ and
$T_{\textit{dust}}$, prestellar clumps have a median ratio
$T_{\textit{kin}}/T_{\textit{dust}}=1.24$, suggesting that these sources are
thermally decoupled. A correlation is found between the evolutionary tracer
$L/M$ and the parameters $T_{\textit{kin}}/T_{\textit{dust}}$ and
$\chi$(NH$_3$) in prestellar sources and protostellar clumps with $L/M<1$
L$_\odot$ M$_\odot^{-1}$. In addition, a weak correlation is found between
non-thermal velocity dispersion and the $L/M$ parameter, possibly indicating an
increase of turbulence with protostellar evolution in the interior of clumps.
Finally, different processes are discussed to explain the differences between
gas and dust temperatures in prestellar candidates, and the origin of
non-thermal motions observed in the clumps.
