A Possible Explanation for the Size Difference of Red and Blue Globular Clusters

Abstract

Most observations of the projected half-light radii of metal-rich globular clusters in a variety of galaxies have shown them to be ~20% smaller than those of their metal-poor counterparts. We show using multimass isotropic Michie-King models that the combined effects of mass segregation and the dependence of main-sequence lifetimes on metallicity can account for this difference, under the assumption that clusters with similar central potentials have the same distribution of half-mass radii. If confirmed, this would represent a new constraint on theories of globular cluster formation and evolution.