We present HST observations that show a bifurcation of colors in the middle main sequence of the globular cluster Omega Centauri. We see this in three different fields, observed with different cameras and filters. We also present high precision photometry of a central ACS field which shows a number of main-sequence turnoffs and subgiant branches. The double main sequence, the multiple turnoffs and subgiant branches, and other population sequences discovered in the past along the red giant branch of this cluster add up to a fascinating but frustrating puzzle. We suggest various explanations, none of them very conclusive.
@article{arxiv.astro-ph/0403112,
title = {Omega Centauri: The Population Puzzle Goes Deeper},
author = {L. R. Bedin and G. Piotto and J. Anderson and S. Cassisi and I. R. King and Y. Momany and G. Carraro and .},
journal= {arXiv preprint arXiv:astro-ph/0403112},
year = {2009}
}
Comments
A_fine_piece_of_work: 12 pages, 2 figures, ApJL_ACCEPTED_, 4 March 2004; high resolution version of the paper available at: ftp://ftp.pd.astro.it/pub/bedin