Velocitydependent Jfactors for annihilation radiation from cosmological simulations
Abstract
We determine the dark matter pairwise relative velocity distribution in a set of Milky Waylike halos in the Auriga and APOSTLE simulations. Focusing on the smooth halo component, the relative velocity distribution is welldescribed by a MaxwellBoltzmann distribution over nearly all radii in the halo. We explore the implications for velocitydependent dark matter annihilation, focusing on four models which scale as different powers of the relative velocity: Sommerfeld, swave, pwave, and dwave models. We show that the Jfactors scale as the moments of the relative velocity distribution, and that the halotohalo scatter is largest for dwave, and smallest for Sommerfeld models. The Jfactor is strongly correlated with the dark matter density in the halo, and is very weakly correlated with the velocity dispersion. This implies that if the dark matter density in the Milky Way can be robustly determined, one can accurately predict the dark matter annihilation signal, without the need to identify the dark matter velocity distribution in the Galaxy.
 Publication:

Journal of Cosmology and Astroparticle Physics
 Pub Date:
 April 2021
 DOI:
 10.1088/14757516/2021/04/070
 arXiv:
 arXiv:2101.06284
 Bibcode:
 2021JCAP...04..070B
 Keywords:

 dark matter simulations;
 dark matter theory;
 hydrodynamical simulations;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  Astrophysics of Galaxies;
 High Energy Physics  Phenomenology
 EPrint:
 25 pages, 11 figures, 2 tables