Upper-left panel: the emission of the SiO J = 5–4 transition from the W51e2 region shown in red and blue corresponding to velocity ranges of 78–159 km s⁻¹ and −54–54 km s⁻¹, respectively. Upper-right panel: the emission of the HC₃N J = 24–23 transition from the W51e2 region shown in red and blue corresponding to velocity ranges of 70–80 km s⁻¹ and 28–49 km s⁻¹, respectively. Lower-left panel: the emission of the SiO J = 5–4 transition from the W51e8 region shown in red and blue corresponding to velocity ranges of 70–82 km s⁻¹ and 4–56 km s⁻¹, respectively. Lower-right panel: the emission of the HC₃N J = 24–23 transition from the W51e8 region shown in red and blue correspond to velocity ranges of 74–84 km s⁻¹ and 29–52 km s⁻¹, respectively. In all these four subfigures, the 1.3 mm continuum is shown in green.