The influence of the radial boundary R_Gal of the DH on the Galactic γ-ray diffuse emission: in the left panel, the CR proton radial distribution along the Galactic disk – also called the CR proton gradient – is displayed for a radial boundary R_Gal of 20 kpc (continuous line) and 30 kpc (dashed line), for the two source profiles L04 in red (Lorimer 2004) and P90 in blue (Paczynski 1990). In the right panel, we have plotted the ratio (map2 − map1)/map1 for each pixel where map1 and map2 were derived with R_Gal = 20 and 30 kpc respectively. The CR source profile is P90 here, all the other inputs being the same as in the reference map of Fig. 1.