On the Anomalous Red Giant Branch of the Globular Cluster ω Centauri

Freyhammer, L. M.; Monelli, M.; Bono, G.; Cunti, P.; Ferraro, I.; Calamida, A.; Degl'Innocenti, S.; Prada Moroni, P. G.; Del Principe, M.; Piersimoni, A.; Iannicola, G.; Stetson, P. B.; Andersen, M. I.; Buonanno, R.; Corsi, C. E.; Dall'Ora, M.; Petersen, J. O.; Pulone, L.; Sterken, C.; Storm, J.
Bibliographical reference

The Astrophysical Journal, Volume 623, Issue 2, pp. 860-865.

Advertised on:
4
2005
Number of authors
20
IAC number of authors
0
Citations
14
Refereed citations
11
Description
We present three different optical and near-infrared (NIR) data sets for evolved stars in the Galactic globular cluster ω Centauri. The comparison between observations and homogeneous sets of stellar isochrones and zero-age horizontal branches provides two reasonable fits. Both of them suggest that the so-called anomalous branch has a metal-intermediate chemical composition (-1.1<=[Fe/H]<=-0.8) and is located ~500 pc beyond the bulk of ω Cen stars. These findings are mainly supported by the shape of the subgiant branch in four different color-magnitude diagrams (CMDs). The most plausible fit requires a higher reddening, E(B-V)=0.155 versus 0.12, and suggests that the anomalous branch is coeval with the bulk of ω Cen stellar populations to within empirical and theoretical uncertainties. This result is supported by the identification of a sample of faint horizontal-branch (HB) stars that might be connected with the anomalous branch. Circumstantial empirical evidence seems to suggest that the stars in this branch form a clump of stars located beyond the cluster. Based on observations made with the ESO Telescopes at the La Silla and Paranal Observatories, program IDs 63.L-0686, 64.N-0038, and 68.D-0545.
Type