Longitude profiles of the 511 keV emission of all nucleosynthesis positrons, with an SN Ia escape fraction of 5% for ⁵⁶Ni positrons and for the three halo GMF configurations (corresponding to the maps in Fig. 3, with an integration range | b | ≤ 10°): no halo field (blue curve), dipole field (black curve), and X-shape field (green curve). The red curve corresponds to the longitude profile of all nucleosynthesis positrons in the absence of propagation, assuming they annihilate in a medium with a positronium fraction of 0.95. The cyan curve corresponds to an analytical model obtained by model fitting to INTEGRAL/SPI observations and given only over the longitude range where data are constraining (see text). The difference in normalisation shows that the positron injection rates used in the model are overestimated by a factor ~2.