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arXiv · 1204.5363

Is there a Size Difference between Red and Blue Globular Clusters?

J. M. B. Downing
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Abstract

Blue (metal-poor) globular clusters are observed to have half-light radii that are ~20% larger than their red (metal-rich) counterparts. The origin of this enhancement is not clear and differences in either the luminosity function or in the actual size of the clusters have been proposed. I analyze a set of dynamically self-consistent Monte Carlo globular cluster simulations to determine the origin of this enhancement. I find that my simulated blue clusters have larger half-light radii due to differences in the luminosity functions of metal-poor and metal-rich stars. I find that the blue clusters can also be physically larger, but only if they have a substantial number of black holes heating their central regions. In this case the difference between half-light radii is significantly larger than observed. I conclude that the observed difference in half-light radii between red and blue globular clusters is due to differences in their luminosity functions and that half-light radius is not a reliable proxy for cluster size.

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J. M. B. Downing. 2012-04-24. Is there a Size Difference between Red and Blue Globular Clusters?. https://doi.org/10.1111/j.1365-2966.2012.21680.x

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