2010MNRAS.402...73B

We report Mopra Australia Telescope National Facility (ATNF), Anglo-Australian Telescope and Atacama Submillimeter Telescope Experiment observations of a molecular clump in Carina, BYF73 = G286.21+0.17, which give evidence of large-scale gravitational infall in the dense gas. From the millimetre and far-infrared data, the clump has a mass of ∼2x10⁴M_☉, luminosity of ∼2-3x10⁴L_☉ and diameter of ∼0.9 pc. From radiative transfer modelling, we derive a mass infall rate of ∼3.4x10^–2M_☉/yr. If confirmed, this rate for gravitational infall in a molecular core or clump may be the highest yet seen. The near-infrared K-band imaging shows an adjacent compact Hii region and IR cluster surrounded by a shell-like photodissociation region showing H₂emission. At the molecular infall peak, the K imaging also reveals a deeply embedded group of stars with associated H₂emission. The combination of these features is very unusual, and we suggest that they indicate the ongoing formation of a massive star cluster. We discuss the implications of these data for competing theories of massive star formation.