A critical look at the merger scenario to explain multiple populations
  and rotation in iron-complex globular clusters
  Merging has been proposed to explain multiple populations in globular
clusters (GCs) where there is a spread in iron abundance (hereafter,
iron-complex GCs). By means of N-body simulations, we investigate if merging is
consistent with the observations of sub-populations and rotation in
iron-complex GCs. The key parameters are the initial mass and density ratios of
the progenitors. When densities are similar, the more massive progenitor
dominates the central part of the merger remnant and the less massive
progenitor forms an extended rotating population. The low-mass progenitor can
become the majority population in the central regions of the merger remnant
only if its initial density is higher by roughly the mass ratio. To match the
radial distribution of multiple populations in two iron-complex GCs ({\omega}
Cen and NGC 1851), the less massive progenitor needs to be four times as dense
as the larger one. Our merger remnants show solid-body rotation in the inner
parts, becoming differential in the outer parts. Rotation velocity V and
ellipticity {\epsilon} are in agreement with models for oblate rotators with
isotropic dispersion. We discuss several kinematic signatures of a merger with
a denser lower mass progenitor that can be tested with future observations.
