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arXiv · 2509.05519

Enhancements in velocity-dependent dark matter annihilation in Galactic subhalos

Odelia V. Hartl·Evan Vienneau·Evan Batteas·Addy J. Evans·Nassim Bozorgnia·Louis E. Strigari
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Abstract

We examine velocity-dependent dark matter annihilation in subhalos using a sample of six Milky Way-like galaxies from the Aurgia simulation suite. We quantify the enhancement in the annihilation rate in subhalos when including the contribution from particles in the smooth component of the halo that overlap with the subhalos. The enhancement in the annihilation rate scales with the smooth component of the host halo dark matter density, and is evident for subhalos over the resolvable mass range. Maximal enhancement factors are ~ 48 for p-wave models, and ~ 37,000 for d-wave models. For p and d-wave annihilation models, ~ 13 and ~ 6 subhalos, respectively, across all six host halos have emission from dark matter annihilation in their direction that is above the foreground emission from the smooth dark matter component, and would therefore be resolvable as sources. Such subhalos with the most significant enhancement factors tend to be on the lower end of the mass range and located closer to the center of the host galaxy. We provide a prescription to calculate the enhancement for subhalos as a function of distance from the Galactic center, and use this to examine the impact on dark matter limits from a couple of example dwarf spheroidals. We show that, including the enhancement factors, limits from individual dwarf spheroidals are at a cross section scale that may approach those derived from the Galactic center.

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Odelia V. Hartl, Evan Vienneau, Evan Batteas, Addy J. Evans, Nassim Bozorgnia, Louis E. Strigari. 2025-09-05. Enhancements in velocity-dependent dark matter annihilation in Galactic subhalos. https://arxiv.org/abs/2509.05519

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