Velocity-dependent J-factors for annihilation radiation from cosmological simulations

Board, Erin; Bozorgnia, Nassim; Strigari, Louis E.; Grand, Robert J.J.; Fattahi, Azadeh; Frenk, Carlos S.; Marinacci, Federico; Navarro, Julio F.; Oman, Kyle A.

Abstract

We determine the dark matter pair-wise relative velocity distribution in a set of Milky Way-like halos in the Auriga and APOSTLE simulations. Focusing on the smooth halo component, the relative velocity distribution is well-described by a Maxwell-Boltzmann distribution over nearly all radii in the halo. We explore the implications for velocity-dependent dark matter annihilation, focusing on four models which scale as different powers of the relative velocity: Sommerfeld, s-wave, p-wave, and d-wave models. We show that the J -factors scale as the moments of the relative velocity distribution, and that the halo-to-halo scatter is largest for d-wave, and smallest for Sommerfeld models. The J -factor 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.

Citation

Board, E., Bozorgnia, N., Strigari, L. E., Grand, R. J., Fattahi, A., Frenk, C. S., Marinacci, F., Navarro, J. F., & Oman, K. A. (2021). Velocity-dependent J-factors for annihilation radiation from cosmological simulations. Journal of Cosmology and Astroparticle Physics, 2021(04), Article 070. https://doi.org/10.1088/1475-7516/2021/04/070

• Journal Article Type: Article
• Acceptance Date: Mar 24, 2021
• Online Publication Date: Apr 27, 2021
• Publication Date: Apr 1, 2021
• Deposit Date: Jul 22, 2021
• Publicly Available Date: Apr 27, 2022
• Journal: Journal of Cosmology and Astroparticle Physics
• Publisher: IOP Publishing
• Peer Reviewed: Peer Reviewed
• Volume: 2021
• Issue: 04
• Article Number: 070
• DOI: https://doi.org/10.1088/1475-7516/2021/04/070
• Public URL: https://durham-repository.worktribe.com/output/1271438
• Related Public URLs: https://arxiv.org/pdf/2101.06284.pdf