Investigating gamma-ray fluxes from globular clusters

TL;DR

This study models and analyzes gamma-ray emissions from 16 globular clusters, confirming detections and setting upper limits, to guide future high-energy observations.

Contribution

It combines numerical modeling with reanalysis of observational data to identify promising globular clusters for gamma-ray detection.

Findings

Confirmed gamma-ray detection of Terzan 5

Set flux upper limits for 15 clusters

Identified top 5 clusters for future observations

Abstract

Globular clusters are large collections of old stars that are orbiting the core of a galaxy. Our Milky Way Galaxy has about 160 known clusters, with perhaps more to be discovered. We first accumulated the necessary parameters for 16 clusters and ran a numerical model that predicts the inverse Compton gamma-ray flux expected from each cluster. We also reanalysed data from 16 clusters observed by the H.E.S.S. very-high-energy (> 100 GeV) gamma-ray telescopes. We confirmed the detection of Terzan 5 and found flux upper limits for the remaining 15 sources that were consistent with published results. We attempted to constrain some source parameters using X-ray and gamma-ray data. We lastly list the five most promising clusters for future observations by the Cherenkov Telescope Array.