2013MNRAS.436.1335L

We present the results of high spatial resolution observations in the 1.1-mm waveband with the Submillimetre Array (SMA) towards the protocluster G10.6-0.4. The 1.1-mm continuum emission reveals seven dense cores. Redshifted absorption dips are seen in the HCN (3-2) lines in these cores, suggesting infalling of gas towards the dense cores. This is the first time that infall has been seen towards multiple sources in a protocluster. We also identified four infrared point sources in this region, which are most likely Class 0/I protostars. Two jet-like structures are also identified from Spitzer/Infrared Array Camera (IRAC) images. The dense core located in the centre has a much larger mass than the off-centre cores. The clump is in overall collapse and the infall motion is supersonic. The standard deviations of core velocities and the velocity differences between the cores and the cloud/clump are all larger than the thermal velocity dispersion. The picture of G10.6-0.4 seems to favour the `competitive accretion' model, but this needs to be tested through further observations.