Distribution of X-ray and radio flux for variations of our sky model. Left panel: we considered a “high amplification model” for the magnetic field and we assumed a uniform gas metallicity of Z = 0.1 Z_⊙ everywhere (instead of Z = 0.3 Z_⊙ as in our baseline model); in the right panel we considered a low-amplification model and a zero metallicity everywhere. The meaning of colours and contours is as in Fig. 5. The text gives more details on the model variations.