Bibcode
Di Cecco, A.; Bono, G.; Stetson, P. B.; Pietrinferni, A.; Becucci, R.; Cassisi, S.; Degl'Innocenti, S.; Iannicola, G.; Prada Moroni, P. G.; Buonanno, R.; Calamida, A.; Caputo, F.; Castellani, M.; Corsi, C. E.; Ferraro, I.; Dall'Ora, M.; Monelli, M.; Nonino, M.; Piersimoni, A. M.; Pulone, L.; Romaniello, M.; Salaris, M.; Walker, A. R.; Zoccali, M.
Bibliographical reference
The Astrophysical Journal, Volume 712, Issue 1, pp. 527-535 (2010).
Advertised on:
3
2010
Journal
Citations
45
Refereed citations
36
Description
We present new empirical estimates of the ΔV bump
HB parameter for 15 Galactic globular clusters (GGCs) using
accurate and homogeneous ground-based optical data. Together with
similar evaluations available in the literature, we ended up with a
sample of 62 GGCs covering a very broad range in metal content (-2.16
dex <= [M/H] <= -0.58 dex). Adopting the homogeneous metallicity
scale provided either by Kraft & Ivans or by Carretta et al., we
found that the observed ΔV bump HB
parameters are larger than predicted. In the metal-poor regime ([M/H]
<~ -1.7, -1.6 dex) 40% of GCs show discrepancies of 2σ
(≈0.40 mag) or more. Evolutionary models that account either for
α- and CNO-enhancement or for helium enhancement do not alleviate
the discrepancy between theory and observations. The outcome is the same
if we use the new solar heavy-element mixture. The comparison between
α- and CNO-enhanced evolutionary models and observations in the
Carretta et al. metallicity scale also indicates that observed ΔV
bump HB parameters, in the metal-rich regime
([M/H] >= 0), might be systematically smaller than predicted.
Based in part on data obtained from the ESO/ST-ECF Science Archive
Facility, from the Isaac Newton Group Archive which is maintained as
part of the CASU Astronomical Data Centre at the Institute of Astronomy,
Cambridge, and from the Canadian Astronomy Data Centre operated by the
National Research Council of Canada with the support of the Canadian
Space Agency.
Related projects
Milky Way and Nearby Galaxies
The general aim of the project is to research the structure, evolutionary history and formation of galaxies through the study of their resolved stellar populations, both from photometry and spectroscopy. The group research concentrates in the most nearby objects, namely the Local Group galaxies including the Milky Way and M33 under the hypothesis
Martín
López Corredoira