Upper panel: the SiO J = 5–4 emission toward W51-IRS2 is shown in red and blue, which correspond to the velocity ranges of 67–97 and −17 to 56 km s⁻¹, while the 1.3 mm continuum emission is presented in green. Lower panel: the HC₃N J = 24–23 emission toward W51-IRS2 shown in red and blue corresponds to the velocity ranges of 66–90 and 39–52 km s⁻¹. The white dashed circles mark a compact source to the east of W51-North (see Sections 3.1.3 and 4.4.1).