How Typical Are The Local Group Dwarf Galaxies?
  We compare the cumulative star formation histories (SFHs) of Local Group (LG)
dwarf galaxies with those in the volume-limited ACS Nearby Galaxy Survey
Treasury (ANGST) sample (D < 4 Mpc), in order to understand how typical the LG
dwarf galaxies are relative to those in the nearby universe. The SFHs were
derived in a uniform manner from high quality optical color-magnitude diagrams
constructed from Hubble Space Telescope imaging. We find that the {\it mean}
cumulative SFHs of the LG dwarfs are comparable to the mean cumulative SFHs of
the ANGST sample for the three different morphological types (dwarf
spheroidals/ellipticals: dSph/dE; dwarf irregulars: dI; transition dwarfs:
dTrans). We also discuss effects such as population gradients and systematic
uncertainties in the stellar models that may influence the derived SFHs. Both
the ANGST and Local Group dwarf galaxies show a consistent and strong
morphology-density relationship, emphasizing the importance of environment in
the evolution of dwarf galaxies. Specifically, we confirm that dIs are found at
lower densities and higher luminosities than dSphs, within this large sample.
We also find that dTrans are located in similar environments to those occupied
by dwarf irregular galaxies, but have systematically lower luminosities that
are more comparable to those of dwarf spheroidals. The similarity of the SFHs
and morphology-density relationships of the LG and ANGST dwarf galaxies
suggests that the LG dwarfs are a good representation of dwarf galaxies in the
local universe.
