Young massive star cluster formation in the Galactic Centre is driven by global gravitational collapse of high-mass molecular clouds
Journal article, 2019
Young massive clusters (YMCs) are the most compact, high-mass stellar systems still forming at the present day. The precursor clouds to such systems are, however, rare due to their large initial gas mass reservoirs and rapid dispersal time-scales due to stellar feedback. None the less, unlike their high-z counterparts, these precursors are resolvable down to the sites of individually forming stars, and hence represent the ideal environments in which to test the current theories of star and cluster formation. Using high angular resolution (1 arcsec / 0.05 pc) and sensitivity ALMA observations of two YMC progenitor clouds in the Galactic Centre, we have identified a suite of molecular line transitions - e.g. c-C3H2 (7 - 6) - that are believed to be optically thin, and reliably trace the gas structure in the highest density gas on star-forming core scales. We conduct a virial analysis of the identified core and proto-cluster regions, and show that half of the cores (5/10) and both proto-clusters are unstable to gravitational collapse. This is the first kinematic evidence of global gravitational collapse in YMC precursor clouds at such an early evolutionary stage. The implications are that if these clouds are to form YMCs, then they likely do so via the 'conveyor-belt' mode, whereby stars continually form within dispersed dense gas cores as the cloud undergoes global gravitational collapse. The concurrent contraction of both the cluster-scale gas and embedded (proto-)stars ultimately leads to the high (proto-)stellar density in YMCs.
stars: formation
Galaxy: centre
ISM: clouds
Author
Ashley T. Barnes
Max Planck Society
Liverpool John Moores University
University of Bonn
S. Longmore
Liverpool John Moores University
A Avison
University of Manchester
UK Atacama Large Millimeter/submillimeter Array Regional Centre Node
Y. Contreras
Leiden University
A. Ginsburg
National Radio Astronomy Observatory
Jonathan D. Henshaw
Max Planck Society
J. M. Rathborne
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
D. L. Walker
Atacama Large Millimeter-submillimeter Array (ALMA)
National Astronomical Observatory of Japan
J. Alves
University of Vienna
J. Bally
University of Colorado
C. Battersby
University of Connecticut
M. T. Beltrán
Arcetri Astrophysical Observatory
H. Beuther
Max Planck Society
Garay Guido
University of Chile (UCH)
L. Gomez
Atacama Large Millimeter-submillimeter Array (ALMA)
J. M. Jackson
National Aeronautics and Space Administration (NASA)
Jouni Kainulainen
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
J. M. D. Kruijssen
Astronomisches Rechen-Institut Heidelberg
X. Lu
National Astronomical Observatory of Japan
E. A. C. Mills
Brandeis University
J. Ott
National Radio Astronomy Observatory
T. Peters
Max Planck Society
Monthly Notices of the Royal Astronomical Society
0035-8711 (ISSN) 1365-2966 (eISSN)
Vol. 486 1 283-303Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
Other Physics Topics
DOI
10.1093/mnras/stz796