Understanding the $\gamma$-ray emission from the globular cluster 47 Tuc: evidence for dark matter?

Abstract

47 Tuc was the first globular cluster observed to be $\gamma$-ray bright, with the $\gamma$-rays being attributed to a population of unresolved millisecond pulsars (MSPs). Recent kinematic data, combined with detailed simulations, appears to be consistent with the presence of an intermediate mass black hole (IMBH) at the centre of 47 Tuc. Building upon this, we analyse 9 years of \textit{Fermi}-LAT observations to study the spectral properties of 47 Tuc with unprecedented accuracy and sensitivity. This 9-year $\gamma$-ray spectrum shows that 47 Tuc's $\gamma$-ray flux cannot be explained by MSPs alone, due to a systematic discrepancy between the predicted and observed flux. Rather, we find a significant preference (TS $=40$) for describing 47 Tuc's spectrum with a two source population model, consisting of an ensemble of MSPs and annihilating dark matter (DM) with an enhanced density around the IMBH, when compared to an MSP-only explanation. The best-fit DM mass of 34 GeV is essentially the same as the best-fit DM explanation for the Galactic centre "excess" when assuming DM annihilation into $b\bar{b}$ quarks. Our work constitutes the first possible evidence of dark matter within a globular cluster.

Accepted to be published as a Rapid Communication in Physical Review D. 6 pages, 2 figures

References in corpus (14)

• Gamma-Ray Emission Concurrent with the Nova in the Symbiotic Binary V407 Cygni
• N-body modeling of globular clusters: Masses, mass-to-light ratios and intermediate-mass black holes
• Multi-Component Dark Matter
• Fermi Establishes Classical Novae as a Distinct Class of Gamma-Ray Sources
• An intermediate-mass black hole in the centre of the globular cluster 47 Tucanae
• HST Proper Motions and Stellar Dynamics in the Core of the Globular Cluster 47 Tucanae
• Production of TeV gamma-radiation in the vicinity of the supermassive black hole in the giant radiogalaxy M87
• Chandra X-Ray Observations of Nineteen Millisecond Pulsars in the Globular Cluster 47 Tucanae
• Long-term observations of the pulsars in 47 Tucanae - II. Proper motions, accelerations and jerks
• Long-term observations of the pulsars in 47 Tucanae. I. A study of four elusive binary systems
• Chandra studies of the globular cluster 47 Tucanae: A deeper X-ray source catalogue, five new X-ray counterparts to millisecond radio pulsars, and new constraints to r-mode instability window
• Dark matter annihilation from intermediate-mass black holes: Contribution to the extragalactic gamma-ray background
• Upper limits on the central black hole masses of 47Tuc and NGC6397
• Gamma-ray Novae: Rare or Nearby?

Cited by in corpus (20)

• Celestial-Body Focused Dark Matter Annihilation Throughout the Galaxy
• Inelastic extra $U(1)$ charged scalar dark matter
• Dark matter searches by the planned gamma-ray telescope GAMMA-400
• Milky Way globular clusters in gamma-rays: analyzing the dynamical formation of millisecond pulsars
• Detecting Axion Dark Matter through the Radio Signal from Omega Centauri
• On the origin of the gamma-ray emission from Omega Centauri: Milisecond pulsars and dark matter annihilation
• Could compact stars in globular clusters constrain dark matter?
• Stellar Shocks From Dark Matter Asteroid Impacts
• Comment on "Understanding the $\gamma$-ray emission from the globular cluster 47 Tuc: evidence for dark matter?"
• Gamma-ray emission from high Galactic latitude globular clusters
• Analysing the radio flux density profile of the M31 galaxy: a possible dark matter interpretation
• Probing the pulsar population of Terzan 5 via spectral modeling
• Upper limits on the dark matter content in globular clusters
• How the dynamical properties of globular clusters impact their $\gamma$-ray and X-ray emission
• What Could be the Observational Signature of Dark Matter in Globular Clusters?
• Assessing Uncertainties in the Predicted Very-High-Energy Flux of Globular Clusters in the Cherenkov Telescope Array Era
• Reply to a comment on `Understanding the gamma-ray emission from the globular cluster 47 Tuc: evidence for dark matter?'
• Improved Treatment of Bosonic Dark Matter Dynamics in Neutron Stars: Consequences and Constraints
• Millisecond Pulsars in Globular Clusters and Implications for the Galactic Center Gamma-Ray Excess
• The Effect of Pulsar Geometry on the Observed Gamma-ray Spectrum of Millisecond Pulsars