The Oldest Globular Clusters in the Large Magellanic Cloud
Abstract
We propose to obtain deep V(F555W) and I(F814W) images of a sample of the metal-poor globular clusters in the Large Magellanic Cloud (LMC). With these observations we will be able to measure the ages of the clusters, which will allow us to place the formation epoch of the initial population of stars in the LMC in the general context of the formation of the Milky Way Galaxy. Specifically, there is mounting data that the Milky Way Galaxy contains two distinct populations of old metal-poor stars: the initial population is a flattened disk with a small amount of rotation that dominates the Population II in the solar neighborhood; and a second population of the same metallicity, which forms a non-rotating spherical halo with an R**-3.5 density law, and is apparently a few Gyrs younger than the first population. The former population is perhaps associated with a spherical collapse model (Eggen, Lynden-Bell, & Sandage 1962) and the latter with a slower cellular accretion model of Searle & Zinn (1978). If the LMC did not form via an ELS process at the same epoch as our Galaxy, then we might expect that the oldest LMC clusters are younger than the oldest components of our Galaxy. There is some evidence for this derived from ground-based photometry for a few of the LMC clusters. We propose to test whether formation of Pop II LMC clusters was indeed delayed by a few Gyr, and in particular to test whether there is coevality between the (mean) ages of the LMC Pop II clusters and clusters in the outer halo of our Galaxy.
- Publication:
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HST Proposal
- Pub Date:
- July 1995
- Bibcode:
- 1995hst..prop.5916S