Mon. Not. R. Astron. Soc., 449, 715-725 (2015/May-1)
Tracing the conversion of gas into stars in Young Massive Cluster Progenitors.
WALKER D.L., LONGMORE S.N., BASTIAN N., KRUIJSSEN J.M.D., RATHBORNE J.M., JACKSON J.M., FOSTER J.B. and CONTRERAS Y.
Abstract (from CDS):
Whilst young massive clusters (YMCs; M ≳ 104 M☉, age ≲ 100 Myr) have been identified in significant numbers, their progenitor gas clouds have eluded detection. Recently, four extreme molecular clouds residing within 200 pc of the Galactic Centre have been identified as having the properties thought necessary to form YMCs. Here, we utilize far-IR continuum data from the Herschel infrared Galactic Plane Survey (HiGAL) and millimetre spectral line data from the Millimetre Astronomy Legacy Team 90 GHz Survey to determine their global physical and kinematic structure. We derive their masses, dust temperatures and radii and use virial analysis to conclude that they are all likely gravitationally bound - confirming that they are likely YMC progenitors. We then compare the density profiles of these clouds to those of the gas and stellar components of the Sagittarius B2 Main and North protoclusters and the stellar distribution of the Arches YMC. We find that even in these clouds - the most massive and dense quiescent clouds in the Galaxy - the gas is not compact enough to form an Arches-like (M = 2x104 M☉, Reff = 0.4 pc) stellar distribution. Further dynamical processes would be required to condense the resultant population, indicating that the mass becomes more centrally concentrated as the (proto)cluster evolves. These results suggest that YMC formation may proceed hierarchically rather than through monolithic collapse.
© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2015)
stars: formation - ISM: clouds - Galaxy: centre - open clusters and associations: general
Clouds b to f (Figure 1) are not in Simbad.
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