Fraction of the (z = 0) in situ stellar mass of galaxies that belongs to three different origins, i.e., sources, as a function of redshift. As above, we split our sample into dwarf (dotted), Milky Way (dot-dashed), and group (dashed) halos. For comparison, in solid curves, we also include the median profile constructed from all central galaxies resolved in the simulation. The fraction of baryonic matter in the main progenitor galaxy is shown in blue, that in satellite galaxies and other halos in orange, and gas in the IGM is shown in green. A dominant fraction of gas forming in situ stars by z = 0 was present in the IGM at high z, while only a low fraction was accreted in a clumpy fashion via satellites. Roughly half of the baryonic mass contributing to the z = 0 in situ stellar mass of galaxies already resides within the main progenitor halo by z ∼ 2.