Our reference map of the diffuse γ-ray emission of the Milky Way at 30 GeV obtained according to the method outlined in Sect. 2. The dominant hadronic component alone is considered. The cosmic ray proton and helium fluxes at the Earth’s osition are taken from Shikaze et al. (2007). These fluxes were retropropagated throughout the DH with the Med model of Table 1. The distribution of primary CR sources in the Galactic disk was borrowed from Lorimer (2004). The differential photon production cross sections of CR protons and helium nuclei impinging on the ISM were parameterized according to Huang et al. (2007). This map is based on the HI and CO 3D Galactic distribution of Pohl et al. (2008). The X_CO factor was set equal to 2.3 × 10²⁰ molecules cm^-2 (K km s^-1)^-1 everywhere in the Galaxy.