Onfall scenario. Top row: gas overabundance profiles in the NSD for [Fe/H]_OA, [Mg/Fe]_OA, and [Eu/Mg]_OA for our fiducial model in the onfall scenario (black solid line). The overabundance is calculated as the difference between the abundance at each radius in the NSD and the abundance just outside the gas-depleted bar region. For comparison, we also show the abundance profile of the competing inflow accretion history treated in Fig. 7 (grey dashed line). We also added the final abundances at the tips of the bar, which are used for the calculation of the overabundance to the plots. Middle row: general evolution of elemental overabundances in the cold gas over time. The lines following each ring are plotted once the mass of the ring exceeds 4 × 10⁶ M_⊙. The dashed line shows the abundance of the accreted gas over time.Bottom row: middle and right panels give the relative abundance plane for magnesium over iron and europium over magnesium, respectively. The final abundance is drawn in solid black and the abundance of the accreted gas as a dashed line. The leftmost panel shows the magnesium abundance plane again, but only for ring 18 at R = 55.5 pc. The timescale is adjusted to start once this ring receives gas from the outer galaxy at t = 4 Gyr.