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The authors would like to thank the referees for their comments which have undoubtedly improved the quality and clarity of the paper. We thank Joe Silk, Cameron Rulten, and Jamie Graham for helpful discussions. We acknowledge the excellent data and analysis tools provided by the Fermi-LAT Collaboration. A.M.B. and P.M.C. acknowledge the financial support of the UK Science and Technology Facilities Council consolidated Grant No. ST/P000541/1. T.L. receives financial support from CNRS-IN2P3 and acknowledges support from the European Unions Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grants No. 690575 and No. 674896, in addition to recurrent institutional funding by CNRS-IN2P3 and the University of Montpellier. This research was supported in part by Perimeter Institute for Theoretical Physics. Research at Perimeter Institute is supported by the Government of Canada through Industry Canada and by the Province of Ontario through the Ministry of Economic Development and Innovation.

Analysis of institutional authors

Lacroix, ThomasAuthor

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Article

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

Publicated to:PHYSICAL REVIEW D. 98 (4): - 2018-08-15 98(4), DOI: 10.1103/PhysRevD.98.041301

Authors: Brown, Anthony M.; Lacroix, Thomas; Lloyd, Sheridan; Boehm, Celine; Chadwick, Paula;

Affiliations

Perimeter Inst, 31 Caroline St North, Waterloo, ON N2L 2Y5, Canada - Author
Univ Durham, Dept Phys, Ctr Adv Instrumentat, South Rd, Durham DH1 3LE, England - Author
Univ Durham, Inst Particle Phys Phenomenol, South Rd, Durham DH1 3LE, England - Author
Univ Montpellier, CNRS, LUPM, F-34160 Montpellier, France - Author
Univ Savoie, CNRS, LAPTH, BP 110, F-74941 Annecy Le Vieux, France - Author
Univ Sydney, Sch Phys, Camperdown, NSW 2006, Australia - Author
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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 appear to be consistent with the presence of an intermediate mass black hole (IMBH) at the center of 47 Tuc. We analyze nine years of Fermi-LAT observations to study the spectral properties of 47 Tuc with unprecedented accuracy and sensitivity. This nine-year.-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 a MSP-only explanation. The best-fit DM mass of 34 GeV is essentially the same as the best-fit DM explanation for the Galactic center excess when assuming DM annihilation into b (b) over bar quarks. Our work constitutes the first possible evidence of dark matter within a globular cluster.

Keywords

47-tucanaeBinariesBlack-holeFermiLong-term observationsMassMillisecond pulsarsProper motionsTelescopeTucanae

Quality index

Bibliometric impact. Analysis of the contribution and dissemination channel

The work has been published in the journal PHYSICAL REVIEW D due to its progression and the good impact it has achieved in recent years, according to the agency WoS (JCR), it has become a reference in its field. In the year of publication of the work, 2018, it was in position 17/69, thus managing to position itself as a Q1 (Primer Cuartil), in the category Astronomy & Astrophysics.

From a relative perspective, and based on the normalized impact indicator calculated from World Citations provided by WoS (ESI, Clarivate), it yields a value for the citation normalization relative to the expected citation rate of: 1.1. This indicates that, compared to works in the same discipline and in the same year of publication, it ranks as a work cited above average. (source consulted: ESI Nov 14, 2024)

This information is reinforced by other indicators of the same type, which, although dynamic over time and dependent on the set of average global citations at the time of their calculation, consistently position the work at some point among the top 50% most cited in its field:

  • Weighted Average of Normalized Impact by the Scopus agency: 1.68 (source consulted: FECYT Feb 2024)
  • Field Citation Ratio (FCR) from Dimensions: 7.7 (source consulted: Dimensions Jun 2025)

Specifically, and according to different indexing agencies, this work has accumulated citations as of 2025-06-17, the following number of citations:

  • WoS: 25
  • Scopus: 29
  • OpenCitations: 19

Impact and social visibility

From the perspective of influence or social adoption, and based on metrics associated with mentions and interactions provided by agencies specializing in calculating the so-called "Alternative or Social Metrics," we can highlight as of 2025-06-17:

  • The use, from an academic perspective evidenced by the Altmetric agency indicator referring to aggregations made by the personal bibliographic manager Mendeley, gives us a total of: 8.
  • The use of this contribution in bookmarks, code forks, additions to favorite lists for recurrent reading, as well as general views, indicates that someone is using the publication as a basis for their current work. This may be a notable indicator of future more formal and academic citations. This claim is supported by the result of the "Capture" indicator, which yields a total of: 8 (PlumX).

With a more dissemination-oriented intent and targeting more general audiences, we can observe other more global scores such as:

  • The Total Score from Altmetric: 3.
  • The number of mentions on the social network X (formerly Twitter): 8 (Altmetric).

It is essential to present evidence supporting full alignment with institutional principles and guidelines on Open Science and the Conservation and Dissemination of Intellectual Heritage. A clear example of this is:

  • The work has been submitted to a journal whose editorial policy allows open Open Access publication.

Leadership analysis of institutional authors

This work has been carried out with international collaboration, specifically with researchers from: Australia; Canada; France; United Kingdom.