Illustration of the spatial regions (here shown in velocity space) contributing to the emergent flux in the S16 model s15p2. The grayscale image shows the observer’s frame flux contribution ∂F_λ,V ∕∂V (the map maximum is saturated at 20% of the true maximum to bias against the strong emission lines and better reveal the origin of the weaker emission) versus wavelength and ejecta velocity. The plot at left connects these emission contributions to ejecta shells and the normalized decay-power deposition profile (dashed line) on the same velocity scale. The upper panel shows the corresponding normalized flux F_λ integrated over all ejecta velocities.