Angular momenta of the pebbles in the fiducial model at the moment of impact with the planet. The individual SAMs of the pebbles are plotted as a function of the pebbles’ initial position within the collision cross-section. In these spin maps, the SAMs of the trajectories in Fig. 3 are highlighted with dots in the respective colours. A dashed green line shows the mean SAM, while the dashed blue lines show the angular momenta of a circular Keplerian orbit. The left panel shows the situation with an atmosphere, while the right panel shows the same pebbles without an atmosphere. The addition of an atmosphere reduces the mean angular momentum from 0.067 to 0.049 l_z,esc, corresponding to a spin frequency of the planet of 0.24 and 0.17 ω_crit, respectively. Without an atmosphere, the individual spin contributions are distributed between the escape angular momentum (l_z/l_z,esc = ±1.00) and the Kepler angular momentum (). In the presence of an atmosphere, nearly all spin contributions are reduced to a sub-Keplerian angular momentum plateau. This suggests a circularisation of the orbits, less tangential impacts, or a combination of the two.