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The orbital phase space of contracted dark matter haloes

Pakmor, Ruediger; Marinacci, Federico; Grand, Robert J.J.; Frenk, Carlos S.; Deason, Alis J.; Cautun, Marius; Callingham, Thomas M.

The orbital phase space of contracted dark matter haloes Thumbnail


Ruediger Pakmor

Federico Marinacci

Robert J.J. Grand

Marius Cautun


We study the orbital phase space of dark matter (DM) haloes in the AURIGA suite of cosmological hydrodynamics simulations of Milky Way (MW) analogues. We characterize haloes by their spherical action distribution, F(Jr,L)⁠, a function of the specific angular momentum, L, and the radial action, Jr, of the DM particles. By comparing DM-only and hydrodynamical simulations of the same haloes, we investigate the contraction of DM haloes caused by the accumulation of baryons at the centre. We find a small systematic suppression of the radial action in the DM haloes of the hydrodynamical simulations, suggesting that the commonly used adiabatic contraction approximation can result in an underestimate of the density by ∼8per cent⁠. We apply an iterative algorithm to contract the AURIGA DM haloes given a baryon density profile and halo mass, recovering the true contracted DM profiles with an accuracy of ∼15per cent⁠, that reflects halo-to-halo variation. Using this algorithm, we infer the total mass profile of the MW’s contracted DM halo. We derive updated values for the key astrophysical inputs to DM direct detection experiments: the DM density and velocity distribution in the Solar neighbourhood.


Pakmor, R., Marinacci, F., Grand, R. J., Frenk, C. S., Deason, A. J., Cautun, M., & Callingham, T. M. (2020). The orbital phase space of contracted dark matter haloes. Monthly Notices of the Royal Astronomical Society, 495(1), 12-28.

Journal Article Type Article
Acceptance Date Jun 16, 2020
Online Publication Date Jun 24, 2020
Publication Date 2020-06
Deposit Date Jun 24, 2020
Publicly Available Date Jun 24, 2020
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 495
Issue 1
Pages 12-28


Published Journal Article (2.7 Mb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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