The in situ origin of the globular cluster NGC 6388 from abundances of
  Sc, V, and Zn of a large sample of stars
  Chemical tagging of globular clusters (GCs) is often done using abundances of
alpha-elements. The iron-peak elements Sc, V, and in particular Zn were
proposed as an alternative to alpha-elements to tag accreted GCs in the
metal-rich regime, where the dwarf galaxy Sagittarius and its GCs show
peculiarly marked under-abundances of these heavier species with respect to
Milky Way stars. A handful of stars in NGC 6388 was used to suggest an accreted
origin for this GC, contradicting the results from dynamics. We tested the
efficiency of the iron-peak method by using large samples of stars in NGC 6388,
compared to thousands of field stars in the disc and the bulge of the Milky
Way. Our abundance ratios of Sc (185 stars) and V (35 stars) for NGC 6388 are
within about 1.5 sigma from the average for the field stars with a similar
metallicity, and they are in perfect agreement for Zn (31 stars), claimed to be
the most sensitive element concerning the accretion pattern. Moreover, the
chemo-dynamical plots, coupled to the bifurcated age-metallicity relation of
GCs in the Galaxy, clearly rule out any association of NGC 6388 to the groups
of accreted GCs. Using a large set of GC abundances from the literature, we
also show that the new method with Sc, V, and Zn seems to be efficient in
picking up GCs related to the Sagittarius dwarf galaxy. Whether this is also
generally true for accreted GCs seems to be less evident, and it should be
verified with larger and homogeneous samples of stars both in the field and in
GCs.
