paper

The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters

arXiv:1008.2755 · doi:10.1088/0004-6256/140/6/1830

Abstract

We present new measurements of the centers for 65 Milky Way globular clusters. Centers were determined by fitting ellipses to the density distribution within the inner $2\arcmin$ of the cluster center, and averaging the centers of these ellipses. The symmetry of clusters was also analyzed by comparing cumulative radial distributions on opposite sides of the cluster across a grid of trial centers. All of the determinations were done with stellar positions derived from a combination of two single-orbit ACS images of the core of the cluster in and . We find that the ellipse-fitting method provides remarkable accuracy over a wide range of core sizes and density distributions, while the symmetry method is difficult to use on clusters with very large cores, or low density. The symmetry method requires a larger field, or a very sharply peaked density distribution.

17 pages, 8 figures, Accepted for publication in AJ, supplementary material will be available upon publication

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