Formation of anomalous globular clusters with metallicity spreads: A
  unified picture
  Recent observations have revealed that at least 8 globular clusters (GCs) in
the Galaxy show internal abundance spreads in [Fe/H]. We investigate the origin
of these `anomalous' GCs using numerical simulations of GCs in the dwarfs
orbiting around the Galaxy and chemical evolution model of dwarfs hosting the
GCs. The principal results are as follows. GCs formed in a host dwarf galaxy
with a total mass of ~ 10^10 M_sun can merge to form a single nuclear GC before
the host is completely destroyed by the Galaxy, if they are massive (> 3*10^5
M_sun) and if they are formed in the inner region (R<400 pc). The GC merger
remnants can capture field stars during its spiral-in to nuclear regions. If
two GCs are formed from star formation events separated by ~300 Myr in their
host dwarf, then the new GC formed from GC merging can have [Fe/H] spread of
0.2 dex and [Ba/Fe] spread of 0.3 dex. GCs formed from GC merging can show
variety of internal abundance spreads depending on the details of their hosts'
chemical evolution. We suggest that anomalous GCs were formed from GC merging
that occurred before the destruction of GC host dwarfs yet after
self-enrichment processes responsible for the observed anti-correlations
between chemical abundances of light elements. We also suggest that the
observed no/little dependence of [Eu/Fe] on [Fe/H] in the Galactic GC M22 is
evidence of massive dwarf galaxies hosting these anomalous GCs.
