Mopra Observations of G305.2+0.2: Massive Star Formation at Different Evolutionary Stages?

We have successfully used a new on-the-fly mapping technique with the Mopra radiotelescope to image G305.2+0.2 in transitions of CO, 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). CO 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 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 CO or HCO emission in the vicinity. We suggest this may be a massive, cold, quiescent and possibly prestellar core.