The Secrets of the Nearest Starburst Cluster. II. The Present-Day Mass Function in NGC 3603

Abstract

Based on deep Very Large Telescope Infrared Spectrometer and ArrayCamera JHK photometry, we have derived the present-day mass function(MF) of the central starburst cluster NGC 3603 YC (Young Cluster) in thegiant H II region NGC 3603. The effects of field contamination,individual reddening, and a possible binary contribution areinvestigated. The MF slopes resulting from the different methods arecompared and lead to a surprisingly consistent cluster MF with a slopeof {Γ}=-0.9+/-0.15. Analyzing different radial annuli around thecluster core, no significant change in the slope of the MF is observed.However, mass segregation in the cluster is evidenced by the increasingdepletion of the high-mass tail of the stellar mass distribution withincreasing radius. We discuss the indications of mass segregation withrespect to the changes observed in the binned and cumulative stellar MFsand argue that the cumulative function, as well as the fraction of high-to low-mass stars, provides better indicators for mass segregation thanthe MF slope alone. Finally, the observed MF and starburst morphology ofNGC 3603 YC are discussed in the context of massive local star-formingregions such as the Galactic center Arches cluster, R136/30 Dor in theLMC, and the Orion Trapezium cluster, all providing resolved templatesfor extragalactic star formation. Despite the similarity in the observedMF slopes, dynamical considerations suggest that the starburst clustersdo not form gravitationally bound systems over a Hubble time. Both theenvironment (gravitational potential of the Milky Way) and theconcentration of stars in the cluster core determine the dynamicalstability of a dense star cluster, such that the long-term evolution ofa starburst is not exclusively determined by the stellar evolution ofits members, as frequently assumed for globular cluster systems.Based on observations obtained at the ESO Very Large Telescope onParanal, Chile, under programs 63.I-0015 and 65.I-0135.