PDFs generated by sampling 1000 times the MAF model for the four galaxy projections in the validation set shown in Fig. 5: NIHAO g8.45e12AGN - halo 136 (a), NIHAO g3.26e13 - halo 20 (b), AURIGA Original_halo_8 - halo 15 (c), and AURIGA Original_halo_21 - halo 29 (d). Contours enclose 68% and 95% of the samples. The colour of the contours varies according to the dataset on which the model has been trained. Dashed grey lines mark the true values of the enclosed mass calculated directly from the simulation.