The Size Difference Between Red And Blue Globular Clusters Is NOT Due To Projection Effects

Abstract

Metal-rich (red) globular clusters in massive galaxies are, on average, smaller than metal-poor (blue) globular clusters. One of the possible explanations for this phenomenon is that the two populations of clusters have different spatial distributions. We test this idea by comparing clusters observed in unusually deep, high signal-to-noise images of M87 with a simulated globular cluster population in which the red and blue clusters have different spatial distributions, matching the observations. We compare the overall distribution of cluster effective radii as well as the relationship between effective radius and galactocentric distance for both the observed and simulated red and blue subpopulations. We find that the different spatial distributions does not produce a significant size difference between the red and blue subpopulations as a whole, or at a given galactocentric distance. These results suggest that the size difference between red and blue globular clusters is likely due to differences during formation or later evolution

14 Pages, 5 figures, Accepted for publication in ApJL

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• Wide-Field Hubble Space Telescope Observations of the Globular Cluster System in NGC1399
• Characteristic radii of the Milky Way Globular Clusters
• How elevated is the dynamical-to-stellar mass ratio of the ultra-compact dwarf S999?
• Luminosity functions of globular clusters in five nearby spiral galaxies using HST/ACS images
• Modifying two-body relaxation in N-body systems by gas accretion