On the origin of the gamma-ray emission from Omega Centauri: Milisecond
  pulsars and dark matter annihilation
  We explore two possible scenarios to explain the observed gamma-ray emission
associated with the atypical globular cluster Omega-Centauri: emission from
millisecond pulsars (MSP) and dark matter (DM) annihilation. In the first case
the total number of MSPs needed to produce the gamma-ray flux is compatible
with the known (but not confirmed) MSP candidates observed in X-rays. A DM
interpretation is motivated by the possibility of Omega-Centauri being the
remnant core of an ancient dwarf galaxy hosting a surviving DM component. At
least two annihilation channels, light quarks and muons, can plausibly produce
the observed gama-ray spectrum. We outline constraints on the parameter space
of DM mass versus the product of the pair-annihilation cross section and
integrated squared DM density (the so-called J-factor). We translate upper
limits on the dark matter content of Omega-Centauri into lower limits on the
annihilation cross section. This shows s-wave annihilation into muons to be
inconsistent with CMB observations, while a small window for annihilation into
light quarks is allowed. Further analysis of Omega-Centauri's internal
kinematics, and/or additional information on the resident MSP population will
yield much stronger constraints and shed light about the origin of this
otherwise mysterious gamma-ray source.
