Amplified J-factors in the Galactic Centre for velocity-dependent dark matter annihilation in FIRE simulations

ABSTRACT We use FIRE-2 zoom cosmological simulations of Milky Way size Galaxy haloes to calculate astrophysical J-factors for dark matter annihilation and indirect detection studies. In addition velocity-independent (s-wave) cross-sections 〈σv〉, we also effective velocity-dependent models, where the cross-section is either p-wave (∝ v2/c2) or d-wave v4/c4). 12 pairs simulations, each run with matter-only (DMO) physics physics. observe FIRE runs produce central velocity dispersions that are systematically larger than in DMO by factors ∼2.5–4. They have a range (∼400 pc) densities (ρFIRE/ρDMO ≃ 0.5–3) owing competing effects baryonic contraction feedback. At 3 deg from Galactic Centre, 3–60 (p-wave) 10–500 (d-wave) times higher runs. The change s-wave signal at more modest can be lower (∼0.3–7), though shape emission profile flatter (less peaked towards Centre) circular on sky Our results broadly consistent assumptions most significantly enhanced compared past estimates. find thermal models may within near future.