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Baryonic effects on the detectability of annihilation radiation from dark matter subhaloes around the Milky Way

Grand, RJJ and White, SDM (2020) Baryonic effects on the detectability of annihilation radiation from dark matter subhaloes around the Milky Way. Monthly Notices of the Royal Astronomical Society, 501 (3). pp. 3558-3567. ISSN 0035-8711

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We use six, high-resolution Λ-cold dark matter (ΛCDM) simulations of galaxy formation to study how emission from dark matter annihilation is affected by baryonic processes. These simulations produce isolated, disc-dominated galaxies with structure, stellar populations, and stellar and halo masses comparable to those of the Milky Way. They resolve dark matter structures with mass above ∼106 M⊙ and are each available in both full-physics and dark-matter-only versions. In the full-physics case, formation of the stellar galaxy enhances annihilation radiation from the dominant smooth component of the galactic halo by a factor of 3, and its central concentration increases substantially. In contrast, subhalo fluxes are reduced by almost an order of magnitude, partly because of changes in internal structure, partly because of increased tidal effects; they drop relative to the flux from the smooth halo by 1.5 orders of magnitude. The expected flux from the brightest Milky Way subhalo is four orders of magnitude below that from the smooth halo, making it very unlikely that any subhalo will be detected before robust detection of the inner Galaxy. We use recent simulations of halo structure across the full ΛCDM mass range to extrapolate to the smallest (Earth-mass) subhaloes, concluding, in contrast to earlier work, that the total annihilation flux from Milky Way subhaloes will be less than that from the smooth halo, as viewed both from the Sun and by a distant observer. Fermi-Large Area Telescope may marginally resolve annihilation radiation from the very brightest subhaloes, which, typically, will contain stars.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2020 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press (OUP)
SWORD Depositor: A Symplectic
Date Deposited: 20 Apr 2023 10:33
Last Modified: 20 Apr 2023 10:33
DOI or ID number: 10.1093/mnras/staa3993
URI: https://researchonline.ljmu.ac.uk/id/eprint/19294
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