Intrinsic iron spread and a new metallicity scale for globular clusters

We have collected spectra of about 2000 red giant branch (RGB) stars in 19 Galactic globular clusters (GC) using FLAMES@VLT (about 100 stars with GIRAFFE and about 10 with UVES, respectively, in each GC). These observations provide an unprecedented, precise, and homogeneous data-set of Fe abundances in GCs. We use it to study the cosmic scatter of iron and find that, as far as Fe is concerned, most GCs can still be considered mono-metallic, since the upper limit to the scatter of iron is less than 0.05 dex, meaning that the degree of homogeneity is better than 12%. The scatter in Fe we find seems to have a dependence on luminosity, possibly due to the well-known inadequacies of stellar atmospheres for…

• NS
  National Science Foundation
• NA
  National Aeronautics and Space Administration
• CI
  California Institute of Technology
• DF
  Deutsche Forschungsgemeinschaft
• MD
  Ministero dell’Istruzione, dell’Università e della Ricerca