Disrupted globular clusters and the gamma-ray excess in the Galactic Centre

Giacomo Fragione*, Fabio Antonini, Oleg Y. Gnedin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

The Fermi Large Area Telescope has provided the most detailed view towards the Galactic Centre (GC) in high-energy gamma-rays. Besides the interstellar emission and point source contributions, the data suggest a residual diffuse gamma-ray excess. The similarity of its spatial distribution with the expected profile of dark matter has led to claims that this may be evidence for dark matter particle annihilation. Here, we investigate an alternative explanation that the signal originates from millisecond pulsars (MSPs) formed in dense globular clusters and deposited at the GC as a consequence of cluster inspiral and tidal disruption. We use a semi-analytical model to calculate the formation, migration, and disruption of globular clusters in the Galaxy. Our model reproduces the mass of the nuclear star cluster and the present-day radial and mass distribution of globular clusters. For the first time, we calculate the evolution of MSPs from disrupted globular clusters throughout the age of the Galaxy and consistently include the effect of theMSP spin-down due to magnetic-dipole braking. The final gamma-ray amplitude and spatial distribution are in good agreement with the Fermi observations and provide a natural astrophysical explanation for the GC excess.

Original languageEnglish (US)
Pages (from-to)5313-5321
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Volume475
Issue number4
DOIs
StatePublished - Apr 21 2018
Externally publishedYes

Keywords

  • Galaxies: star clusters: general
  • Galaxy: centre
  • Galaxy: kinematics and dynamics
  • Gamma-rays: diffuse background
  • Gamma-rays: galaxies
  • Pulsars: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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