2006MNRAS.365..321W

We have successfully used a new on-the-fly mapping technique with the Mopra radio telescope to image G305.2+0.2 in transitions of ¹³CO, HCO⁺, N₂H⁺, CH₃CN and CH₃OH. All these species appear to be concentrated towards the infrared-quiet methanol maser site G305A (G305.21+0.21). We suggest that this region contains an extremely deeply embedded site of massive star formation, with comparable qualities to the low-mass Class 0 stage. The infrared-bright methanol maser site G305B (G305.21+0.20) also exhibits emission in all the mapped transitions, but always at a lower level. We suggest this is because it harbours a site of massive star formation older and more developed than G305.21+0.21. All transitions appear to be extended beyond the size of the Mopra beam (30 arcsec). ¹³CO and HCO⁺ line wings are suggestive of an outflow in the region, but the spatial resolution of these data is insufficient to identify the powering source. A narrow-lined (1.6 km/s compared to a typical line FWHM of 6.4 km/s) N₂H⁺ source (G305SW) is found 90 arcsec to the south-west of the main star-forming centres, which does not correspond to any CH₃CN or CH₃OH source, nor does it correspond well to ¹³CO or HCO⁺ emission in the vicinity. We suggest this may be a massive, cold, quiescent and possibly pre-stellar core.