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Halo Substructure Boosts to the Signatures of Dark Matter Annihilation

1
GRAPPA Institute, Institute of Physics, University of Amsterdam, 1098 XH Amsterdam, The Netherlands
2
Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo, Kashiwa 277-8583, Japan
3
Institute of Management and Information Technologies, Chiba University, Chiba 263-8522, Japan
4
Institute for Cosmic Ray Research, University of Tokyo, Kashiwa 277-8582, Japan
5
Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
6
RIKEN Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS), Wako 351-0198, Japan
*
Author to whom correspondence should be addressed.
Galaxies 2019, 7(3), 68; https://doi.org/10.3390/galaxies7030068
Received: 27 March 2019 / Revised: 24 June 2019 / Accepted: 26 June 2019 / Published: 1 July 2019
(This article belongs to the Special Issue The Role of Halo Substructure in Gamma-Ray Dark Matter Searches)
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Abstract

The presence of dark matter substructure will boost the signatures of dark matter annihilation. We review recent progress on estimates of this subhalo boost factor—a ratio of the luminosity from annihilation in the subhalos to that originating the smooth component—based on both numerical N-body simulations and semi-analytic modelings. Since subhalos of all the scales, ranging from the Earth mass (as expected, e.g., the supersymmetric neutralino, a prime candidate for cold dark matter) to galaxies or larger, give substantial contribution to the annihilation rate, it is essential to understand subhalo properties over a large dynamic range of more than twenty orders of magnitude in masses. Even though numerical simulations give the most accurate assessment in resolved regimes, extrapolating the subhalo properties down in sub-grid scales comes with great uncertainties—a straightforward extrapolation yields a very large amount of the subhalo boost factor of ≳100 for galaxy-size halos. Physically motivated theoretical models based on analytic prescriptions such as the extended Press-Schechter formalism and tidal stripping modeling, which are well tested against the simulation results, predict a more modest boost of order unity for the galaxy-size halos. Giving an accurate assessment of the boost factor is essential for indirect dark matter searches and thus, having models calibrated at large ranges of host masses and redshifts, is strongly urged upon. View Full-Text
Keywords: halo substructure; dark matter annihilation; indirect dark matter searches; subhalo boost halo substructure; dark matter annihilation; indirect dark matter searches; subhalo boost
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Ando, S.; Ishiyama, T.; Hiroshima, N. Halo Substructure Boosts to the Signatures of Dark Matter Annihilation. Galaxies 2019, 7, 68.

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