Formation redshift of the baryons that form the in situ stellar populations z = 0 galaxies (blue). We also compare to the formation redshifts of the dark matter halo (solid green) and the dark matter halo core (dashed green). Solid curves show all origins, while the dashed (dotted) blue line shows mass accreted via mergers (the IGM). For comparison, we also show the mean age of all (in situ) stars of the central galaxy in orange (red). While the global dark matter (DM) halo as well as its core assemble earlier for less massive objects, the inverse holds for the stellar population, as well as the accretion of baryons that later fuel in situ star formation.