Age and mass segregation of multiple stellar populations in galactic
  nuclei and their observational signatures
  Nuclear stellar cluster (NSCs) are known to exist around massive black holes
(MBHs) in galactic nuclei. They are thought to have formed through in-situ star
formation following gas inflow to the nucleus of the galaxy and/or through the
infall of multiple stellar clusters. Here we study the latter, and explore the
composite structure of the NSC, and its relation to the various stellar
populations originating from its progenitor infalling clusters. We use N-body
simulations of clusters infall, and show that this scenario may produce
observational signatures in the form of age segregation: the distribution of
the stellar properties (e.g. stellar age and/or metallicity) in the NSCs
reflect the infall history of the different clusters. The stellar populations
of clusters infalling at different times (dynamical ages), are differentially
segregated in the NSC, and are not fully mixed even after few Gyrs of
evolution. Moreover, the radial properties of stellar populations in the
progenitor cluster are mapped to their radial distribution in the final NSC,
potentially leading to efficient mass segregation in NSCs, even those where
relaxation times are longer than a Hubble time. Finally, the overall structures
of the stellar populations present non-spherical configurations and show
significant cluster to cluster population differences.
