Toy simulation of spectrogram of typical Hα-emitting disk galaxy at z ∼ 0.9 (intrinsic spectrum in uppermost panel, spatial profile on the leftmost panels) as observed with an HST-like slitless spectrograph, but with an improved spectral resolution of ℛ ∼ 2500 (see text). Top: without kinematic effects; bottom: signature of the intrinsic velocity field is clearly visible as a distortion of the spectrogram. The red dashed lines correspond to the galaxy rotation curves at each emission lines’ position, and are tracing the distortion in the spectrogram.