Second generation stellar disks in Dense Star Clusters and cluster
  ellipticities
  Globular Clusters (GCs) and Nuclear Star Clusters (NSCs) are typically
composed by several stellar populations, characterized by different chemical
compositions. Different populations show different ages in NSCs but not
necessarily in GCs. The youngest populations in NSCs appear to reside in
disk-like structures, as observed in our Galaxy and in M31. Gas infall followed
by formation of second generation (SG) stars in GCs may similarly form
disk-like structures in the clusters nuclei. Here we explore this possibility
and follow the long term evolution of stellar disks embedded in GCs, and study
their effects on the evolution of the clusters. We study disks with different
masses by means of detailed N-body simulations and explore their morphological
and kinematic signatures on the GC structures. We find that as a second
generation disk relaxes, the old, first generation, stellar population flattens
and becomes more radially anisotropic, making the GC structure become more
elliptical. The second generation stellar population is characterized by a
lower velocity dispersion, and a higher rotational velocity, compared with the
primordial older population. The strength of these kinematic signatures depends
both on the relaxation time of the system and on the fractional mass of the
second generation disk. We therefore conclude that SG populations formed in
flattened configurations will give rise to two systematic trends: (1) Positive
correlation between GC ellipticity and fraction of SG population (2) Positive
correlation between GC relaxation time and ellipticity. Thereby GC
ellipticities and rotation could be related to the formation of SG stars and
their initial configuration.
