Galactic Diffuse Gamma Rays—Recalculation Based on New Measurements of the Cosmic Electron Spectrum

In this work, we revisit the all-sky Galactic diffuse γ-ray emission taking into account new measurements of the cosmic ray (CR) electron/positron spectrum by PAMELA, ATIC, and Fermi, which show excesses of cosmic electrons/positrons beyond the expected fluxes in the conventional model. Since the origins of the extra electrons/positrons are not clear, we consider three different scenarios to account for the excesses: astrophysical sources such as Galactic pulsars, dark matter (DM) decay, and DM annihilation. Further, new results from Fermi-LAT on the (extra-)Galactic diffuse γ-rays are adopted. The background CRs without the new sources give lower diffuse γ-rays compared to the Fermi-LAT observation, which is consistent with previous analysis. The scenario with astrophysical sources predicts diffuse γ-rays with little difference with the background. The DM annihilation models with τ^± final state are disfavored by the Fermi diffuse γ-ray data, while there are only a few constraints on the decaying DM scenario. Furthermore, there is always a bump at higher energies (~TeV) of the diffuse γ-ray spectra for the DM scenarios due to final state radiation. Finally, we find that the Fermi-LAT diffuse γ-ray data can be explained by simply enlarging the normalization of the electron spectrum without introducing any new sources, which may indicate that the current constraints on the DM models can be much stronger given a precise background estimate.