DYNAMICAL MASS ESTIMATES FOR FIVE YOUNG MASSIVE STELLAR CLUSTERS

摘要: We have obtained high-dispersion spectra for four massive star clusters in the dwarf irregular galaxies NGC 4214 and 4449, using HIRES spectrograph on Keck I telescope. Combining velocity dispersions of with structural parameters photometry from images taken Hubble Space Telescope, we estimate mass-to-light (M/L) ratios compare these simple stellar population models order to constrain mass functions (MFs) clusters. For all find M/L values that are similar or slightly higher than a Kroupa MF thereby rule out any is deficient low-mass stars compared Kroupa-type MF. The virial masses ranging between 2.1 × 105 1.5 106 M⊙, half-light radii 3.0 5.2 pc, estimated core densities range 2 103 M⊙ pc-3, ages 200 800 Myr. also present new near-infrared spectroscopy luminous young (~15 Myr) cluster nearby spiral galaxy 6946, which previously observed HIRES. measurements infrared agree well previous estimates dispersion this cluster, yielding about 1.7 M⊙. Including an improved reddening toward data yield excellent agreement cluster. properties studied here consistent being versions old globular found around major galaxies.