A large difference in the progenitor masses of active and passive
  galaxies in the EAGLE simulation
  Cumulative number density matching of galaxies is a method to observationally
connect descendent galaxies to their typical main progenitors at higher
redshifts and thereby to assess the evolution of galaxy properties. The
accuracy of this method is limited due to galaxy merging and scatter in the
stellar mass growth history of individual galaxies. Behroozi et al. (2013) have
introduced a refinement of the method, based on abundance matching of observed
galaxies to the Bolshoi dark-matter-only simulation. The EAGLE cosmological
hydro-simulation is well suited to test this method, because it reproduces the
observed evolution of the galaxy stellar mass function and the passive
fraction. We find agreement with the Behroozi et al. (2013) method for the
complete sample of main progenitors of z = 0 galaxies, but we also find a
strong dependence on the current star formation rate. Passive galaxies with a
stellar mass up to 10^10.75 Msun have a completely different median mass
history than active galaxies of the same mass. This difference persists if we
only select central galaxies. This means that the cumulative number density
method should be applied separately to active and passive galaxies. Even then,
the typical main progenitor of a z = 0 galaxy already spans two orders of
magnitude in stellar mass at z = 2.
