Extragalactic diffuse γ-rays from dark matter annihilation: revised prediction and full modelling uncertainties

Abstract

Abstract. Recent high-energy data from Fermi-LAT on the diffuse γ-ray background have been used to set among the best constraints on annihilating TeV cold dark matter candidates. In order to assess the robustness of these limits, we revisit and update the calculation of the isotropic extragalactic γ-ray intensity from dark matter annihilation. The emission from halos with masses ≥ 10 10 M provides a robust lower bound on the predicted intensity. The intensity including smaller halos whose properties are extrapolated from their higher mass counterparts is typically 5 times higher, and boost from subhalos yields an additional factor ∼ 1.5. We also rank the uncertainties from all ingredients and provide a detailed error budget for them. Overall, our fiducial intensity is a factor 5 lower than the one derived by the Fermi-LAT collaboration in their latest analysis. This indicates that the limits set on extragalactic dark matter annihilations could be relaxed by the same factor. We also calculate the expected intensity for self-interacting dark matter in massive halos and find the emission reduced by a factor 3 compared to the collisionless counterpart. The next release of the CLUMPY code will provide all the tools necessary to reproduce and ease future improvements of this prediction.

Searching for dark matter annihilation from individual halos: uncertainties, scatter and signal-to-noise ratios

“…We will present our own version of this calculation below, and show that it agrees well with other recent estimates, [e.g. 78,[98][99][100][101]. An alternative approach is to model the clustering or density distribution of dark matter particles at a statistical level, calibrating to simulations [e.g.…”

“…There have been many previous calculations of the substructure boost factor, starting with [47] and [48]. Here we compare our results to five recent versions of the calculation, by Bartels & Ando [99], Han et al [98], Stref & Lavalle [100], Moline et al [78], and Huetten et al [101]. Generally, these models all assume spherical halos and subhalos with NFW profiles (truncated at a tidal radius, in the case of the subhalos), and a power-law subhalo mass function.…”

“…Finally, [101] explore the sensitivity of the boost factor to different assumptions, as part of their calculation of the extragalactic gamma-ray background (EGB). Their default (conservative) model predicts a fairly low substructure boost factor (∼ 5) on cluster scales, but this is partly due to taking α = −1.9, a fairly low normalization for the substructure mass function, and the low concentration-mass relation of [85].…”

γ-ray and ν Searches for Dark-Matter Subhalos in the Milky Way with a Baryonic Potential

“…CLUMPY v2.0 [5] was used for this purpose, to estimate the sensitivity of the CTA [1] and HAWC [27] γ-ray telescopes to galactic DM subhalos. Aside from galactic subhalo studies, CLUMPY has also been used by several teams to model DM annihilation or decay in γ-rays or ν in many targets: dwarf spheroidal galaxies [37][38][39][40][41][42][43][44][45][46], the galactic halo [47][48][49], the Smith HI cloud [50], nearby galaxies [51], galaxy clusters [52][53][54], and also for the extragalactic diffuse emission [55].…”

Cosmological boost factor for dark matter annihilation at redshifts of $z=10$-$100$ using the power spectrum approach

“…where the cosmological boost factor is defined as B(z) ≡ 1 + δ 2 (x; z) . Two methods have been used to calculate B(z): the halo-model approach (e.g., [12][13][14][15][16][17]) and the power spectrum (PS) approach [18,19]. Both approaches give consistent results (e.g.…”