Molecular envelope around the HII region RCW 120
  The H II region RCW120 is a well-known object, which is often considered as a
target to verify theoretical models of gas and dust dynamics in the
interstellar medium. However, the exact geometry of RCW120 is still a matter of
debate. In this work, we analyse observational data on molecular emission in
RCW120 and show that 13CO(2-1) and C18O(2-1) lines are fitted by a 2D model
representing a ring-like face-on structure. The changing of the C18O(3-2) line
profile from double-peaked to single-peaked from the dense molecular
Condensation 1 might be a signature of stalled expansion in this direction. In
order to explain a self-absorption dip of the 13CO(2-1) and 13CO(3-2) lines, we
suggest that RCW120 is surrounded by a diffuse molecular cloud, and find
confirmation of this cloud on a map of interstellar extinction. Optically thick
13CO(2-1) emission and the infrared 8 um PAH band form a neutral envelope of
the H II region resembling a ring, while the envelope breaks into separate
clumps on images made with optically thin C18O(2-1) line and far-infrared dust
emission.
