|Authors||R. de Grijs (1), G.F. Gilmore (1), A.D. Mackey (1), M.I., Wilkinson (1), S.F. Beaulieu (2), R.A. Johnson (3), , B.X., Santiago (4)|
|Affiliation||1 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA |
2 Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, BC, V8P 1A1, Canada
3 European Southern Observatory, Casilla 19001, Santiago 19, Chile
4 Universidade Federal do Rio Grande do Sul, Instituto de Física, 91501-970 Porto Alegre, RS Brazil
|Submitted to||Monthly Notices of the Royal Astronomical Society|
Our results are based on Hubble Space Telescope/WFPC2 observations of six rich star clusters in the LMC, selected to include three pairs of clusters of similar age, mass, metallicity, and distance from the LMC centre, exhibiting a large spread in core radii between the clusters in each pair.
All clusters show clear evidence of mass segregation: (i) their luminosity function slopes steepen with increasing cluster radius, and (ii) the brighter stars are characterized by smaller core radii. For all sample clusters, both the slope of the luminosity function in the cluster centres and the degree of mass segregation are similar to each other, within observational errors of a few tenths of power-law slope fits to the data. This implies that their initial mass functions must have been very similar, down to ~0.8 - 1.0 Mo.
We rule out variations in the IMF as the main driver of the increasing spread of cluster core radii with cluster age. We propose instead that external tidal effects generate the range of core properties seen.