Mass and size growth of early-type galaxies by dry mergers in cluster
  environments
  We perform dry merger simulations to investigate the role of dry mergers in
the size growth of early-type galaxies in high density environments. We replace
the virialized dark matter haloes obtained by a large cosmological $N$-body
simulation with $N$-body galaxy models consisting of two components, a stellar
bulge and a dark matter halo, which have higher mass resolution than the
cosmological simulation. We then re-simulate nine cluster forming regions,
whose masses range from 1e+14 Msun to 5e+14 Msun. Masses and sizes of stellar
bulges are also assumed to satisfy the stellar mass--size relation of high-z
compact massive early-type galaxies. We find that dry major mergers
considerably contribute to the mass and size growth of central massive
galaxies. One or two dry major mergers double the average stellar mass and
quadruple the average size between $z=2$ and $z=0$. These growths favorably
agree with observations. Moreover, the density distributions of our simulated
central massive galaxies grow from the inside-out, which is consistent with
recent observations. The mass--size evolution is approximated as R propto
M_{*}^{alpha}, with alpha ~ 2.24. Most of our simulated galaxies are
efficiently grown by dry mergers, and their stellar mass--size relations match
the ones observed in the local Universe. Our results show that the central
galaxies in the cluster haloes are potential descendants of high-z (z ~ 2-3)
compact massive early-type galaxies. This conclusion is consistent with
previous numerical studies which investigate the formation and evolution of
compact massive early-type galaxies.
