Hα profile from RCW50. The profile can be decomposed in three ways (panels 1–3). The axes are the V_LSR in km s⁻¹ (X axis) and intensity in arbitrary units (Y axis). The profile, in addition to the night sky lines (labeled “N”), can be decomposed into either one component (panel 1) or two components (panels 2 and 3), labeled “0” and “1”. The solid and dash dotted lines are the observed and the fitted profiles, respectively.