Formation of massive globular clusters with dark matter and its
  implication on dark matter annihilation
  Recent observational studies of $\gamma$-ray emission from massive globular
clusters (GCs) have revealed possible evidence of dark matter (DM) annihilation
within GCs. It is, however, still controversial whether the emission comes from
DM or from milli-second pulsars. We here present the new results of numerical
simulations, which demonstrate that GCs with DM can originate from nucleated
dwarfs orbiting the ancient MW. The simulated stripped nuclei (i.e., GCs) have
the central DM densities ranging from 0.1 to several ${\rm M_\odot pc^{-3}}$,
depending on the orbits and the masses of the host dwarf galaxies. However, GCs
born outside the central regions of their hosts can have no/little DM after
their hosts are destroyed and the GCs become the Galactic halo GCs. These
results suggest that only GCs originating from stellar nuclei of dwarfs can
possibly have DM. We further calculate the expected $\gamma$-ray emission from
these simulated GCs and compare them to observations of $\omega$ Cen. Given the
large range of DM densities in the simulated GCs, we suggest that the recent
possible detection of DM annihilation from GCs should be more carefully
interpreted.
