Discovery of Large-Scale Gravitational Infall in a Massive Protostellar Cluster

TL;DR

This paper presents observational evidence of large-scale gravitational infall in a massive protostellar cluster, suggesting a potentially highest-ever infall rate, and discusses its implications for theories of massive star formation.

Contribution

It provides the first detailed observational evidence of large-scale gravitational infall in a massive star-forming region, with a high infall rate and associated star formation features.

Findings

Mass infall rate ~ 3.4 x 10^-2 Msun yr-1

Detection of a deeply embedded star group with H2 emission

Evidence supporting ongoing formation of a massive star cluster

Abstract

We report Mopra (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 mass ~ 2 x 10^4 Msun, luminosity ~ 2-3 x 10^4 Lsun, and diameter ~ 0.9 pc. From radiative transfer modelling, we derive a mass infall rate ~ 3.4 x 10^-2 Msun 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 HII 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 they indicate the ongoing formation of a massive star cluster. We discuss the implications of these data for competing theories of massive star formation.