Ellipticities at R(h) of LMC star clusters

The projected ellipticities of 53 populous LMC star clusters have been derived by means of PDS 1010A scans and a computer interactive method of reduction implemented on an Apollo 570 workstation. Film copies of a pair of J and U plates taken with the 1.2 m UK Schmidt Telescope in Australia were used. The ellipticities derived here agree with those found by previous investigators, when comparisons were possible at the same radius. Ellipticity variations within individual globular clusters are seen to be a common phenomenon, so the ellipticities e(h) at a distance corresponding to the half-mass radius R(h) from the center were adopted to represent the cluster's flatness. Using these values for the LMC clusters, it is found that LMC clusters are more elliptical than those of the Galaxy. Although the young LMC globular clusters show a tendency to be more elliptical than the old ones, there is no strong evidence for a significant difference among them. Finally, e(h) was found to increase with the total mass of the clusters, possibly indicating that high-mass clusters have higher angular momentum, or have more difficulty in shedding angular momentum, than do low mass clusters, and remain longer in their initial flattened shape. 18 refs