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The signal of decaying dark matter with hydrodynamical simulations

Lovell, Mark R; Barnes, David; Bahé, Yannick; Schaye, Joop; Schaller, Matthieu; Theuns, Tom; Bose, Sownak; Crain, Robert A; Vecchia, Claudio dalla; Frenk, Carlos S; Hellwing, Wojciech; Kay, Scott T; Ludlow, Aaron D; Bower, Richard G

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David Barnes

Yannick Bahé

Joop Schaye

Sownak Bose

Robert A Crain

Claudio dalla Vecchia

Wojciech Hellwing

Scott T Kay

Aaron D Ludlow

Richard G Bower


Dark matter particles may decay, emitting photons. Drawing on the EAGLE family of hydrodynamic simulations of galaxy formation – including the APOSTLE and C-EAGLE simulations – we assess the systematic uncertainties and scatter on the decay flux from different galaxy classes, from Milky Way satellites to galaxy clusters, and compare our results to studies of the 3.55 keV line. We demonstrate that previous detections and non-detections of this line are consistent with a dark matter interpretation. For example, in our simulations the width of the the dark matter decay line for Perseus-analogue galaxy clusters lies in the range 1300-1700 kms−1, and exceptionally up to 3000 kms−1. Therefore, the non-detection of the 3.55 keV line in the centre of the Perseus cluster by the Hitomi collaboration is consistent with detections by other instruments. We also consider trends with stellar and halo mass and evaluate the scatter in the expected fluxes arising from the anisotropic halo mass distribution and from object-to-object variations. We provide specific predictions for observations with XMM-Newton and with the planned X-ray telescopes XRISM and ATHENA. If future detections of unexplained X-ray lines match our predictions, including line widths, we will have strong evidence that we have discovered the dark matter.


Lovell, M. R., Barnes, D., Bahé, Y., Schaye, J., Schaller, M., Theuns, T., …Bower, R. G. (2019). The signal of decaying dark matter with hydrodynamical simulations. Monthly Notices of the Royal Astronomical Society, 485(3), 4071-4089.

Journal Article Type Article
Acceptance Date Feb 21, 2019
Online Publication Date Mar 8, 2019
Publication Date May 31, 2019
Deposit Date Mar 12, 2019
Publicly Available Date Mar 27, 2019
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 485
Issue 3
Pages 4071-4089


Published Journal Article (2.1 Mb)

Copyright Statement
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.

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