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Dark matter annihilation radiation in hydrodynamic simulations of Milky Way haloes.

Schaller, Matthieu and Frenk, Carlos S. and Theuns, Tom and Calore, Francesca and Bertone, Gianfranco and Bozorgnia, Nassim and Crain, Robert A. and Fattahi, Azadeh and Navarro, Julio F. and Sawala, Till and Schaye, Joop (2016) 'Dark matter annihilation radiation in hydrodynamic simulations of Milky Way haloes.', Monthly notices of the Royal Astronomical Society., 455 (4). pp. 4442-4451.


We obtain predictions for the properties of cold dark matter annihilation radiation using high-resolution hydrodynamic zoom-in cosmological simulations of Milky Way-like galaxies (APOSTLE project) carried out as part of the ‘Evolution and Assembly of GaLaxies and their Environments’ (EAGLE) programme. Galactic haloes in the simulation have significantly different properties from those assumed in the ‘standard halo model’ often used in dark matter detection studies. The formation of the galaxy causes a contraction of the dark matter halo, whose density profile develops a steeper slope than the Navarro–Frenk–White (NFW) profile between r ≈ 1.5 kpc and r ≈ 10 kpc. At smaller radii, r ≲ 1.5 kpc, the haloes develop a flatter than NFW slope. This unexpected feature may be specific to our particular choice of subgrid physics model but nevertheless the dark matter density profiles agree within 30 per cent as the mass resolution is increased by a factor 150. The inner regions of the haloes are almost perfectly spherical (axis ratios b/a > 0.97 within r = 1 kpc) and there is no offset larger than 45 pc between the centre of the stellar distribution and the centre of the dark halo. The morphology of the predicted dark matter annihilation radiation signal is in broad agreement with γ-ray observations at large Galactic latitudes (b ≳ 3°). At smaller angles, the inferred signal in one of our four galaxies is similar to that which is observed but it is significantly weaker in the other three.

Item Type:Article
Keywords:Methods: numerical, Galaxy: centre, Cosmology: theory, Dark matter, Gamma-rays: galaxies.
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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:10 November 2015
Date deposited:23 February 2016
Date of first online publication:09 December 2015
Date first made open access:No date available

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