  We analyze the carbon monoxide emission around the star WR 16 aiming to
chieve a better understanding of the interaction between massive stars with
their surroundings. We study the molecular gas in a region of 86.'4 x 86.'4 in
size using CO (J=1-0) and 13CO (J=1-0) line data obtained with the 4-m NANTEN
telescope. Radio continuum archival data at 4.85 GHz, obtained from the
Parkes-MIT-NRAO Southern Radio Survey, are also analyzed to account for the
ionized gas. Available IRAS (HIRES) 60 and 100 microns images are used to study
the characteristics of the dust around the star. Our new CO and 13CO data allow
the low/intermediate density molecular gas surrounding the WR nebula to be
completely mapped. We report two molecular features at -5 km/s and -8.5 km/s
(component 1 and component 2, respectively) having a good morphological
resemblance with the Halpha emission of the ring nebula. Component 2 seems to
be associated with the external ring, whilst component 1 is placed at the
interface between component 2 and the Halpha emission. We also report a third
molecular feature 10' in size (component 3) at a velocity of -9.5 km/s having a
good morphological correspondence with the inner optical and IR emission,
although high resolution observations are recommended to confirm its existence.
The stratified morphology and kinematics of the molecular gas could be
associated to shock fronts and high mass-loss events related to different
evolutive phases of the WR star, which have acted upon the surrounding
circumstellar molecular gas. An analysis of the mass of component 1 suggests
that this feature is composed by swept-up interstellar gas and is probably
enriched by molecular ejecta. The direction of the proper motion of WR 16
suggests that the morphology of the inner ring nebula is induced by the stellar
motion.
