Numerical simulations of dwarf galaxy merger trees
  We investigate the evolution of dwarf galaxies using N -body/SPH simulations
that incorporate their formation histories through merger trees constructed
using the ex- tended Press-Schechter formalism. The simulations are
computationally cheap and have high spatial resolution. We compare the
properties of galaxies with equal final mass but with different merger
histories with each other and with those of observed dwarf spheroidals and
irregulars. We show that the merger history influences many observable dwarf
galaxy proper- ties. We identify two extreme cases that make this influence
stand out most clearly: (i) merger trees with one massive progenitor that grows
through relatively few mergers and (ii) merger trees with many small
progenitors that merge only quite late. At a fixed halo mass, a type (i) tree
tends to produce galaxies with larger stellar masses, larger half-light radii,
lower central surface brightness, and since fewer potentially an- gular
momentum cancelling mergers are required to build up the final galaxy, a higher
specific angular momentum, compared with a type (ii) tree. We do not perform
full-fledged cosmological simulations and therefore cannot hope to reproduce
all observed properties of dwarf galaxies. However, we show that the simulated
dwarfs are not unsimilar to real ones.
