Comparison of the velocity residuals of our model: around the sun’s original location at the original time (top row - as shown in Fig. 7); at the sun’s reflection point, Sun_RP, at the original time (second row); around the sun’s location, 10 Myrs earlier than the original time (third row); and finally, around the sun’s location, 10 Myrs later than the original time (bottom row). The first two columns present the tangential and radial velocity residuals for the stars, while the two last columns show those of the gas. The ridges of the spiral arm segments, extracted from the respective sharpened images, are overlaid in black for the stellar ridges and grey for the gas ridges.