The Sizes of Globular Clusters in NGC 4278

Christopher Usher (Swinburne University of Technology)

We have used ACS imaging to study the sizes of globular clusters around the early type galaxy NGC 4278. We find that the size of globular clusters increases with distance from the centre of NGC 4278. This relationship is expected as the size of a globular cluster is strongly effected by the tidal field it experiences. We also see that redder globular clusters are smaller than bluer ones. Since the mean colour of globular clusters become bluer with increasing distance it is unclear it whether the size difference between blue and red globular clusters is due to a combination of the colour-distance and distance-size relationships or is due to an intrinsic size dependence on colour. When we compare the ratio of the mean sizes of blue globular clusters to the mean sizes of red ones in bins of distance from NGC 4278, we find that the ratio is independent of distance showing that the size of globular clusters does depend on their colour and not just on their location with in their host galaxy

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