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The signal of decaying dark matter with hydrodynamical simulations.

Lovell, Mark R. and Barnes, David and Bahé, Yannick and Schaye, Joop and Schaller, Matthieu and Theuns, Tom and Bose, Sownak and Crain, Robert A. and Vecchia, Claudio dalla and Frenk, Carlos S. and Hellwing, Wojciech and Kay, Scott T. and Ludlow, Aaron D. and Bower, Richard G. (2019) 'The signal of decaying dark matter with hydrodynamical simulations.', Monthly notices of the Royal Astronomical Society., 485 (3). pp. 4071-4089.


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.

Item Type:Article
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Publisher statement:© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.
Date accepted:21 February 2019
Date deposited:12 March 2019
Date of first online publication:08 March 2019
Date first made open access:17 June 2021

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