Spectral evolution of the γ-ray emissivities per gas nucleon in the Eridu (green), Reticulum (red), and North Hydrus (cyan) clouds. The orange curve gives the average q_LIS emissivity measured in the atomic gas at latitudes 10° ≤ |b| ≤ 70° (Casandjian 2015). The emissivities are shown for the HI optical-depth correction that best fits the γ-ray data (T_s = 100 K for Eridu, 140 K for q_LIS, and optically thin for the others). The shaded bands include the statistical and systematic uncertainties.