Ivan R. King

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Aims. We present a detailed study of the radial distribution of the multiple populations identified in the Galactic globular cluster ω Cen. Methods. We used both space-based images (ACS/WFC and WFPC2) and ground-based images (FORS1@VLT and WFI@2.2m ESO telescopes) to map the cluster from the inner core to the outskirts (∼20 arcmin). These data sets have(More)
From deep color–magnitude arrays made from V and I images taken with Hubble Space Telescope's WFPC2 camera we have determined luminosity functions (LFs) down to a level that corresponds to ∼0.13 M ⊙ , for the low-metal-abundance globular clusters M15, M30, M92, and NGC 6397. Because of the similarity of the metallicities of these clusters, differences in(More)
Accurate photometry with HST's ACS shows that the main sequence of the globular cluster NGC 2808 splits into three separate branches. The three MS branches may be associated with complexities of the cluster's horizontal branch and of its abundance distribution. We attribute the MS branches to successive rounds of star formation, with different helium(More)
We present the results of a deep Hubble Space Telescope (HST) exposure of the nearby glob-ular cluster NGC 6397, focussing attention on the cluster's white dwarf cooling sequence. This sequence is shown to extend over 5 magnitudes in depth, with an apparent cutoff at magnitude F 814W ∼ 27.6. We demonstrate, using both artificial star tests and the(More)
In the old, populous, and metal-rich open cluster NGC 6791 we have used deep HST/ACS images to track the white dwarf cooling sequence down to m F606W ≃ 28.5. The white dwarf luminosity function shows a well defined peak at m F606W ≃ 27.4, and a bending to the blue in the color–magnitude diagram. If this peak corresponds to the end of the white dwarf cooling(More)
Collisions and mergers of gas-rich galaxies trigger bursts of star and cluster formation. Of the thousands of clusters typically formed during a major merger, only the most massive and compact survive for Gi-gayears as globular clusters (GCs). In ∼ <1 Gyr old merger remnants, these 'second-generation' GCs appear by the hundreds as young halo clusters of ∼(More)