Discovery of large-scale gravitational infall in a massive protostellar cluster

• Published in: Monthly notices of the Royal Astronomical Society 2010-02, Vol.402 (1), p.73-86
• Main Authors: Barnes, Peter J., Yonekura, Yoshinori, Ryder, Stuart D., Hopkins, Andrew M., Miyamoto, Yosuke, Furukawa, Naoko, Fukui, Yasuo
• Format: Article
• Language: English
• Subjects: astrochemistry; Astronomy; Astrophysics; Earth, ocean, space; Exact sciences and technology; infrared: ISM; ISM: kinematics and dynamics; ISM: molecules; radio lines: ISM; Star & galaxy formation; stars: formation
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2009.15890.x

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 ∼2 × 104 M⊙, luminosity of ∼2–3 × 104 L⊙ and diameter of ∼0.9 pc. From radiative transfer modelling, we derive a mass infall rate of ∼3.4 × 10−2 M⊙ yr−1. 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 H ii region and IR cluster surrounded by a shell-like photodissociation region showing H2 emission. At the molecular infall peak, the K imaging also reveals a deeply embedded group of stars with associated H2 emission. 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.