tokens: in size. The spectra were reduced with NOSTAR 2 using the standard procedure. For the molecular analysis, we also used SEST CO(2-1) data that were kindly provided to us by A. P. Marston in 2008 (see Marston et al. 1999 ), and NANTEN CO(1-0) obtained in 2001 (see Paper I ). 3.2 H <sc>i</sc> and radio continuum data Current radio surveys are of little use to inspect the surroundings of WR16 with enough resolution and sensitivity. In Paper I , the radio continuum data at 4.8 GHz were obtained from the Parkes-MIT-NRAO (PMN) survey. At the location of WR16, the survey contains observations performed with the Parkes 64-m antenna. However, the beam size (∼5 arcmin × 5 arcmin) is comparable to the diameter of the ring nebula (≲8 arcmin), which hampers a detailed study. To render an acceptable resolution, observations must be performed using interferometeric techniques, and only two radio interferometers, the Australia Telescope Compact Array (ATCA) and the Molonglo Observatory Synthesis Telescope (MOST), offer public surveys covering an area compatible with the Galactic longitude of WR16. The Southern Galactic Plane Survey (SGPS; McClure-Griffiths et al. 2005 ), which includes both H i and continuum emission data from the ATCA, is limited to −1° ≤ b ≤ +1°, and WR16 lies more than 1° away south of this band. On the other hand, the radio continuum emission towards WR16 at 843 MHz from the Molonglo Galactic Plane Survey (MGPS-2; Murphy et al. 2007 ) is affected by strong sidelobes introduced by the bright nearby H ii region RCW 46. To obtain the best possible set of maps, we then processed from scratch archival radio observations performed during 2001 and 2002 towards this region with the Australia Telescope Compact Array (ATCA) in the configurations EW 352 and EW 367 under project C961. The region was observed simultaneously in the H i 21-cm line and in radio continuum. The continuum data consist of 32 channels spanning through a bandwidth of 128 MHz centred at 1384 MHz, while the H i line was recorded over 1024 channels covering a 4 MHz bandwidth (equivalent to 0.82 km s −1 ). Pointings were arranged in an hexagonal mosaic with a 23 arcmin grid separation and were observed as snapshots during 60 s over a wide range of hour angles. All observation parameters are summarized in Table 1 . Table 1. Parameters of ATCA observations. Standard data reduction was performed with the miriad software package (Sault, Teuben Wright 1995 ), using PKS B1934−638 for flux and bandpass calibration and PKS B0843−54 for phase calibration. For the H i data, the continuum component was subtracted by fitting a linear baseline through a set of line-free channels in the Fourier domain. All pointings in the mosaic were cleaned together with a joint approach using the miriad task MOSMEM. For the H i data, the solutions converged for all channels. Finally, the clean components were convolved with a 130 arcsec × 130 arcsec and a 100 arcsec × 100 arcsec beam for the line and
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