Spatial SFR of the high- (solid lines) and low-α (dashed lines) sequences. The high-α sequence formed in the inner disc (<10 kpc) and its bulk SFR moved outwards until finishing 6 Gyr ago. The low-α sequence began forming in the inner disc 8–10 Gyr ago and moved outwards with time. The overlap at a given radius and time between the sequences stems from the age uncertainty (see Fig. A.4.).