Precise abundance analysis of the outer halo globular cluster M 75
  Globular clusters (GCs) are the oldest stellar systems in the Milky Way. Long
time considered as simple stellar populations, nowadays we recognize their
complex star formation history through precise abundance analysis of a variety
of chemical elements in individual cluster members. Although we do not
necessarily see clues for multiple populations in all GC colour-magnitude
diagrams, all GCs present significant spreads and certain anticorrelations
between their light and alpha element abundances. Furthermore, the heavy
element abundances in individual stars of the primordial generation and their
comparison to halo field stars and dwarf galaxies could provide us with
valuable information about the very first stars that could have formed in GCs.
M75 is a unique outer halo (galactocentric distance of ~15 kpc) GC with a
peculiar Horizontal Branch morphology. Here we present the first abundance
measurements of 16 individual red giants from high resolution spectroscopy. The
cluster is metal rich ([Fe/H] = -1.17 +/- 0.02), alpha-enhanced, and shows a
marginal spread in [Fe/H] of 0.07 dex, typical of most GCs of similar
luminosity. The O-Na anticorrelation is clearly visible, showing at least two
generations of stars, formed on a short timescale. We also discuss r- and
s-process element abundances in the context of the earliest cluster enrichment
phases.
