Effective J -factor of the Galactic Center for velocity-dependent dark matter annihilation

Abstract

We present the effective J-factors for the Milky Way for scenarios in which dark matter annihilation is p-wave or d-wave suppressed. We find that the velocity suppression of dark matter annihilation can have a sizable effect on the morphology of a potential dark matter annihilation signal in the Galactic Center. The gamma-ray flux from the innermost region of the Galactic Center is in particular suppressed. We find that for dark matter density profiles with steep inner slopes, the morphology of the inner Galaxy gamma-ray emission in p-wave models can be made similar to the morphology in standard s-wave models. This similarity may suggest that model discrimination between s-wave and p-wave is challenging, for example, when fitting the Galactic Center excess. However, we show that it is difficult to simultaneously match s-and p-wave morphologies at both large and small angular scales. The J-factors we calculate may be implemented with astrophysical foreground models to self-consistently determine the morphology of the excess with velocity-suppressed dark matter annihilation.

Angular distribution of gamma-ray emission from velocity-dependent dark matter annihilation in subhalos

“…For the larger values of n, the scale free angular distribution is increasingly suppressed at both large and smallθ. This finding is consistent with previous results studying the angular distribution of gamma-ray emission from dark matter annihilation in the Milky Way halo [17]. The suppression arises because dark matter particle velocities tend to be suppressed both close to and far from the subhalo center.…”

“…There has been recent renewed interest in extending these limits by examining the effects of velocitydependent dark matter annihilation on the flux of gamma rays emitted by astrophysical objects with high dark matter densities [11][12][13][14][15][16][17][18]. In particular, for velocitydependent annihilation, the standard factorization of the gamma-ray flux into an astrophysical contribution (the J-factor) and a particle physics contribution fails, because the dark matter annihilation cross section is nontrivially correlated with the dark matter velocity distribution.…”

Strong constraints on light dark matter interpretation of the EDGES signal

“…The approach taken by [4][5][6] as well as in CMB studies of DM-hydrogen interaction [13,14,26,27] is a modelindependent one, where one assumes the above velocity dependence in the cross section without specifying its origin. In light of recent advancements it is natural to ask whether there exists a particle physics model that can address the EDGES observation while being consistent with the existing limits.…”

Dark matter spectra from the electroweak to the Planck scale

“…For instance, the annihilation cross-section could depend on the relative DM velocity, which varies between astrophysical systems. In such a case, however, an effective factorization can still be achieved and so the discussion of this sections ports over directly, although the velocity dependence of the cross-section is now placed into the astrophysics factor, see e.g [89]…”