Ivo Saviane, Gary S. Da Costa, Enrico V. Held, Veronica Sommariva, Marco Gullieuszik, Beatriz Barbuy, Sergio Ortolani
Well determined radial velocities and abundances are essential for analyzing
the properties of the Globular Cluster system of the Milky Way. However more
than 50% of these clusters have no spectroscopic measure of their metallicity.
In this context, this work provides new radial velocities and abundances for
twenty Milky Way globular clusters which lack or have poorly known values for
these quantities. The radial velocities and abundances are derived from spectra
obtained at the Ca II triplet using the FORS2 imager and spectrograph at the
VLT, calibrated with spectra of red giants in a number of clusters with well
determined abundances. For about half of the clusters in our sample we present
significant revisions of the existing velocities or abundances, or both. We
also confirm the existence of a sizable abundance spread in the globular
cluster M54, which lies at the center of the Sagittarius dwarf galaxy. In
addition evidence is provided for the existence of a small intrinsic internal
abundance spread (sigma [Fe/H](int) ~ 0.11-0.14 dex, similar to that of M54) in
the luminous distant globular cluster NGC 5824. This cluster thus joins the
small number of Galactic globular clusters known to possess internal
metallicity ([Fe/H]) spreads.
View original:
http://arxiv.org/abs/1202.1304
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