A preliminary survey of collapsed cores in the Magellanic Clouds' globular clusters

Abstract

We present a preliminary report on a surface photometry survey for collapsed cores in the Magellanic Clouds’ globular clusters. We give core morphology classifications for the 33 globular clusters examined so far. One cluster, NGC 2019, shows definite signs of a collapsed core, and two others, NGC 1774 and NGC 1951, appear as strong candidates. This detection of postcollapse cores outside the Milky Way opens some interesting prospects for future dynamical studies. However, the fraction of collapsed-core clusters appears to be smaller in the Magellanic Clouds than in the Galaxy. This may be due in part to their younger ages, or to the limitations imposed by the seeing effects. It is also possible that the relative scarcity reflects the physical difference in the tidal field environments between the Galaxy and the Clouds, in agreement with a trend found earlier, viz., that the tidal shocks from disk passages accelerate dynamical evolution and enhance the propensity for core collapse.