paper

The contribution to Galactic Centre γ-ray excess from cluster-born millisecond pulsars. Constraints from direct N-body simulations

arXiv:2603.06239 · doi:10.1051/0004-6361/202557963

Abstract

The Galactic Centre γ-ray excess (GCE), observed by Fermi-LAT around Sgr A*, exceeds expectations from standard cosmic-ray models and is commonly attributed either to dark matter annihilation or to unresolved millisecond pulsars (MSPs). We revisit the MSP scenario within a fully dynamical framework by tracking neutron stars (NSs) formed in globular clusters (GCs) and deposited into the central kiloparsec. Using high-resolution direct N-body simulations of GCs evolving in a time-dependent Milky Way potential, we model both present-day clusters and an early population of disrupted systems. From the simulated NS distributions, we infer the MSP population via an empirically calibrated MSP-to-NS ratio and construct mock γ-ray flux profiles assuming representative pulsar luminosities. MSPs associated with surviving clusters already produce a substantial γ-ray contribution, while disrupted clusters enhance both the amplitude and central concentration of the signal. Under reasonable assumptions, the combined MSP population reproduces the observed GCE properties, favouring an astrophysical origin over dark matter interpretations.

arXiv comment10 pages, 8 figures, accepted by A&A

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