Significant structures and velocities of RCW 49. Upper panel: mutliwavelength views of RCW 49. The white arrows point to Hα patches with positive velocity and the green contour delineates the arc-like feature. The white dashed circle underlines the circular radio emission feature. Lower panel: velocity (in km s⁻¹) of the different components (sorted by decreasing peak intensities) of the Hα profiles averaged over the areas shown. Coordinates are Galactic (in degrees). Zones dominated by negative (positive) velocity are shown in yellow (green). Values in red have similar intensities while values in blue indicate profiles fitted with a single component. The symbol “ ” indicates that the component has a FWHM ≥ 35 km s⁻¹. The magenta, black, and red stars indicate the positions of Wd2, WR21a, and Collinder 220, respectively.