On the possible correlation of Galactic VHE source locations and
  enhancements of the surface density in the Galactic plane
  The association of very-high energy sources with regions of the sky rich in
dust and gas has been noticed in the study of individual VHE sources. However,
the statistical significance of such correlation for the whole population of
TeV detections has not been assessed yet. Here we present a study of the
association of VHE sources in the central Galactic region with positions of
enhanced material content. We obtain estimates of the material content through
two classical tracers: dust emission and intensity of the
$^\textrm{12}$CO(1$\rightarrow$0) line. We make use of the recently released
all-sky maps of astrophysical foregrounds of the Planck Collaboration and of
the extensive existing CO mapping of the Galactic sky. In order to test the
correlation, we construct randomized samples of VHE source positions starting
from the inner Galactic plane survey sources detected by the H.E.S.S. array. We
find hints of a positive correlation between positions of VHE sources and
regions rich in molecular material, which in the best of cases reaches the
3.9sigma level. The latter confidence is however decreased if variations in the
selection criteria are considered, what lead us to conclude that a positive
correlation cannot be firmly established yet. Forthcoming VHE facilities will
be needed in order to firmly establish the correlation.
