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

## TL;DR

This paper investigates whether gamma-ray emission from Omega Centauri is due to millisecond pulsars or dark matter annihilation, analyzing observational data and theoretical models to identify the most plausible source.

## Contribution

It compares MSP and dark matter scenarios for gamma-ray emission in Omega Centauri, providing constraints on dark matter properties and highlighting the need for further observational data.

## Key findings

- MSP population could explain gamma-ray flux consistent with X-ray observations.
- Dark matter annihilation into muons is incompatible with CMB constraints.
- A narrow parameter space allows dark matter annihilation into light quarks.

## 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.