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arXiv · 1907.06682

On the origin of the gamma-ray emission from Omega Centauri: Milisecond pulsars and dark matter annihilation

Javier Reynoso-Cordova·Oleg Burgueño·Alex Geringer-Sameth·Alma X. Gonzalez-Morales·Stefano Profumo·O. Valenzuela
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Abstract

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.

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Javier Reynoso-Cordova, Oleg Burgueño, Alex Geringer-Sameth, Alma X. Gonzalez-Morales, Stefano Profumo, O. Valenzuela. 2019-07-15. On the origin of the gamma-ray emission from Omega Centauri: Milisecond pulsars and dark matter annihilation. https://doi.org/10.1088/1475-7516%2F2021%2F02%2F010

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