The Secrets of the Nearest Starburst Cluster: Ii. the Present-day Mass Function in Ngc 3603

Based on deep VLT/ISAAC JHK photometry, we have derived the presentday mass function of the central starburst cluster NGC3603YC (Young Cluster) in the giant Hii region NGC3603. The effects of field contamination, individual reddening, and a possible binary contribution are investigated. The MF slopes resulting from the different methods are compared, and lead to a surprisingly consistent cluster MF with a slope of Γ = −0.9 ± 0.15. Analyzing different radial annuli around the cluster core, no significant change in the slope of the MF is observed. However, mass segregation in the cluster is evidenced by the increasing depletion of the high-mass tail of the stellar mass distribution with increasing radius. We discuss the indications of mass segregation with respect to the changes observed in the binned and cumulative stellar mass functions, and argue that the cumulative function as well as the fraction of highto low-mass stars provide better indicators for mass segregation than the MF slope alone. Finally, the observed mass function and starburst morphology of NGC3603YC is discussed in the context of massive local star-forming regions such as the Galactic Center Arches cluster, R 136/30 Dor in the LMC, and the Orion Trapezium cluster, all providing resolved templates for extragalactic star formation. Despite the similarity in the observed MF slopes, dynamical considerations suggest that the starburst clusters do not form gravitationally bound systems over a Hubble time. Both the environment (gravitational potential of the Milky Way) and the concentration of stars in the cluster core determine the dynamical stability of a dense star cluster, such that the long-term evolution of a starburst is not exclusively determined by the stellar evolution of its members, as frequently assumed for globular cluster systems. Subject headings: HII regions: individual (NGC 3603) — open clusters and associations: individual (NGC 3603, HD 97950) — stars: pre-main-sequence – stars: mass