Avoiding progenitor bias: The structural and mass evolution of Brightest
  Group and Cluster Galaxies in Hierarchical models since z~1
  The mass and structural evolution of massive galaxies is one of the hottest
topics in galaxy formation. This is because it may reveal invaluable insights
into the still debated evolutionary processes governing the growth and assembly
of spheroids. However, direct comparison between models and observations is
usually prevented by the so-called "progenitor bias", i.e., new galaxies
entering the observational selection at later epochs, thus eluding a precise
study of how pre-existing galaxies actually evolve in size. To limit this
effect, we here gather data on high-redshift brightest group and cluster
galaxies, evolve their (mean) host halo masses down to z=0 along their main
progenitors, and assign as their "descendants" local SDSS central galaxies
matched in host halo mass. At face value, the comparison between high redshift
and local data suggests a noticeable increase in stellar mass of a factor of >2
since z~1, and of >2.5 in mean effective radius. We then compare the inferred
stellar mass and size growth with those predicted by hierarchical models for
central galaxies, selected at high redshifts to closely match the halo and
stellar mass bins as in the data. Only hierarchical models characterized by
very limited satellite stellar stripping and parabolic orbits are capable of
broadly reproducing the stellar mass and size increase of a factor ~2-4
observed in cluster galaxies since z ~1. The predicted, average (major) merger
rate since z~1 is in good agreement with the latest observational estimates.
