IC4499 revised: spectro-photometric evidence of small light-element
  variations
  It has been suggested that IC4499 is one of the very few old globulars to not
host multiple populations with light-element variations. To follow-up on this
very interesting result, here we make use of accurate HST photometry and
FLAMES@VLT high-resolution spectroscopy to investigate in more detail the
stellar population properties of this system. We find that the red giant branch
of the cluster is clearly bimodal in near-UV -- optical colour-magnitude
diagrams, thus suggesting that IC4499 is actually composed by two
sub-populations of stars with different nitrogen abundances. This represents
the first detection of multiple populations in IC4499. Consistently, we also
find that one star out of six is Na-rich to some extent, while we do not detect
any evidence of intrinsic spread in both Mg and O. The number ratio between
stars with normal and enriched nitrogen is in good agreement with the number
ratio - mass trend observed in Galactic globular clusters. Also, as typically
found in other systems, nitrogen rich stars are more centrally concentrated
than normal stars, although this result cannot be considered conclusive because
of the limited field of view covered by our observations (~$1r_h$). On the
contrary, we observe that both the RGB UV color spread, which is a proxy of N
variations, and Na abundance variations, are significantly smaller than those
observed in Milky Way globular clusters with mass and metallicity comparable to
IC4499. The modest N and Na spreads observed in this system can be tentatively
connected to the fact that IC4499 likely formed in a disrupted dwarf galaxy
orbiting the Milky Way, as previously proposed based on its orbit.
