Accurate photometry with HST/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 abundances; we discuss possible sources of helium enrichment. Some other massive globulars also appear to have complex populations; we compare them with NGC 2808.
@article{arxiv.astro-ph/0703767,
title = {A Triple Main Sequence in the Globular Cluster NGC 2808},
author = {G. Piotto and L. R. Bedin and J. Anderson and I. R. King and S. Cassisi and A. P. Milone and S. Villanova and A. Pietrinferni and A. Renzini},
journal= {arXiv preprint arXiv:astro-ph/0703767},
year = {2010}
}
Comments
13 pages, 3 figures, 1 table. Accepted for publication in ApJ Letter, on March 29 2007