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Cosmic particle colliders : simulations of self-interacting dark matter with anisotropic scattering.

Robertson, A. and Massey, R. and Eke, V. (2017) 'Cosmic particle colliders : simulations of self-interacting dark matter with anisotropic scattering.', Monthly notices of the Royal Astronomical Society., 467 (4). pp. 4719-4730.


We investigate how self-interacting dark matter (SIDM) with anisotropic scattering affects the evolution of isolated dark matter haloes as well as systems with two colliding haloes. For isolated haloes, we find that the evolution can be adequately captured by treating the scattering as isotropic, as long as the isotropic cross-section is appropriately matched to the underlying anisotropic model. We find that this matching should not be done using the momentum transfer cross-section, as has been done previously. Matching should instead be performed via a modified momentum transfer cross-section that takes into account that dark matter particles can be relabelled after they scatter, without altering the dynamics. However, using cross-sections that are matched to give the same behaviour in isolated haloes, we find that treating dark matter scattering as isotropic underpredicts the effects of anisotropic dark matter scattering when haloes collide. In particular, the DM-galaxy offset induced by SIDM in colliding galaxy clusters is larger when we simulate the underlying particle model, than if we use a matched isotropic model. On the other hand, well-motivated particle models with anisotropic scattering typically have cross-sections with a strong velocity dependence, and we discover a previously unrecognised effect that suppresses DM-galaxy offsets in colliding clusters making it hard for these systems to provide competitive constraints on such particle models.

Item Type:Article
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Publisher statement:This article has been published in Monthly Notices of the Royal Astronomical Society ©: 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:19 February 2017
Date deposited:17 May 2017
Date of first online publication:22 February 2017
Date first made open access:17 May 2017

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