2004/01/31 by F. R. Ferraro, A. Sollima, E. Pancino +4 · 1 citation
Physics and Astronomy · #Astro and Planetary Science #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/383149
published as Astrophys.J. 603 (2004) L81-L84 · ApJL, in press
openalex publication_date 2004/02/17 · arxiv created 2004/02/26 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/01
Using deep high-resolution multiband images taken with the Very Large Telescope and the Hubble Space Telescope , we discovered a new anomalous sequence in the color-magnitude diagram of ω Cen. This feature appears as a narrow well-defined subgiant branch (SGB-a), which merges into the main sequence of the dominant cluster population at a magnitude significantly fainter than the cluster turnoff (TO). The simplest hypothesis assumes that the new feature is the extension of the anomalous red giant branch (RGB-a) metal-rich population discovered by Lee et al. and Pancino et al. However, under this assumption the interpretation of the SGB-a does not easily fit into the context of a self-enrichment scenario within ω Cen. In fact, its TO magnitude, shape, and extension are not compatible with a young metal-rich population, as required by the self-enrichment process. The TO level of the SGB-a suggests indeed an age as old as the main cluster population, further supporting the extracluster origin of the most metal-rich stars, as suggested by Ferraro, Bellazzini, & Pancino. Only accurate measurements of radial velocities and metal abundances for a representative sample of stars will firmly establish whether or not the SGB-a is actually related to the RGB-a and will finally shed light on the origin of the metal-rich population of ω Cen.