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

Brown, Anthony M.; Lacroix, Thomas; Lloyd, Sheridan; Bœhm, Céline; Chadwick, Paula

doi:10.1103/physrevd.98.041301

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

Brown, Anthony M.; Lacroix, Thomas; Lloyd, Sheridan; Bœhm, Céline; Chadwick, Paula

Authors

Dr Anthony Brown anthony.brown@durham.ac.uk
Assistant Professor

Thomas Lacroix

Dr Sheridan Lloyd sheridan.j.lloyd@durham.ac.uk
Postdoctoral Research Associate

Céline Bœhm

Professor Paula Chadwick p.m.chadwick@durham.ac.uk
Head Of Department

Abstract

47 Tuc was the first globular cluster observed to be γ -ray bright, with the γ 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 γ -ray spectrum shows that 47 Tuc’s γ -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 quarks. Our work constitutes the first possible evidence of dark matter within a globular cluster.

Citation

Brown, A. M., Lacroix, T., Lloyd, S., Bœhm, C., & Chadwick, P. (2018). Understanding the γ-ray emission from the globular cluster 47 Tuc: Evidence for dark matter?. Physical Review D, 98(4), Article 041301(R). https://doi.org/10.1103/physrevd.98.041301

Journal Article Type	Article
Acceptance Date	Jun 1, 2018
Online Publication Date	Aug 3, 2018
Publication Date	Aug 3, 2018
Deposit Date	Aug 7, 2018
Publicly Available Date	Aug 8, 2018
Journal	Physical Review D
Print ISSN	2470-0010
Electronic ISSN	2470-0029
Publisher	American Physical Society
Peer Reviewed	Peer Reviewed
Volume	98
Issue	4
Article Number	041301(R)
DOI	https://doi.org/10.1103/physrevd.98.041301
Related Public URLs	https://arxiv.org/abs/1806.01866

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Copyright Statement
Reprinted with permission from the American Physical Society: Brown, Anthony M., Lacroix, Thomas, Lloyd, Sheridan, Bœhm, Céline & Chadwick, Paula (2018). Understanding the γ-ray emission from the globular cluster 47 Tuc: Evidence for dark matter? Physical Review D 98(4): 041301(R). © (2018) by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modified, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.