Dwarf galaxy populations in present-day galaxy clusters - II. The
  history of early-type and late-type dwarfs
  How did the dwarf galaxy population of present-day galaxy clusters form and
grow over time? We address this question by analysing the history of dark
matter subhaloes in the Millennium-II cosmological simulation. A semi-analytic
model serves as the link to observations. We argue that a reasonable analogue
to early morphological types or red-sequence dwarf galaxies are those subhaloes
that experienced strong mass loss, or alternatively those that have spent a
long time in massive haloes. This approach reproduces well the observed
morphology-distance relation of dwarf galaxies in the Virgo and Coma clusters,
and thus provides insight into their history. Over their lifetime, present-day
late types have experienced an amount of environmental influence similar to
what the progenitors of dwarf ellipticals had already experienced at redshifts
above two. Therefore, dwarf ellipticals are more likely to be a result of early
and continuous environmental influence in group- and cluster-size haloes,
rather than a recent transformation product. The observed morphological
sequences of late-type and early-type galaxies have developed in parallel, not
consecutively. Consequently, the characteristics of today's late-type galaxies
are not necessarily representative for the progenitors of today's dwarf
ellipticals. Studies aiming to reproduce the present-day dwarf population thus
need to start at early epochs, model the influence of various environments, and
also take into account the evolution of the environments themselves.
