  We study dwarf galaxies in the Centaurus A group to investigate their
metallicity and possible environmental effects. The Centaurus A group (at ~4
Mpc from the Milky Way) contains about 50 known dwarf companions of different
morphologies and stellar contents, thus making it a very interesting target to
study how these galaxies evolve. Here we present results for the early-type
dwarf galaxy population in this group. We use archival HST/ACS data to study
the resolved stellar content of 6 galaxies, together with isochrones from the
Dartmouth stellar evolutionary models. We derive photometric metallicity
distribution functions of stars on the upper red giant branch via isochrone
interpolation. The 6 galaxies are moderately metal-poor (<[Fe/H]>=-1.56 to
-1.08), and metallicity spreads are observed (internal dispersions of
sigma_[Fe/H]=0.10 to 0.41 dex). We also investigate the possible presence of
intermediate-age stars, and discuss how these affect our results. The dwarfs
exhibit flat to weak radial metallicity gradients. For the two most luminous,
most metal-rich galaxies, we find statistically significant evidence for at
least two stellar subpopulations: the more metal-rich stars are found in the
center of the galaxies, while the metal-poor ones are more broadly distributed
within the galaxies. We find no clear trend of the derived physical properties
as a function of (present-day) galaxy position in the group, which may be due
to the small sample we investigate. We compare our results to the early-type
dwarf population of the Local Group, and find no outstanding differences,
despite the fact that the Centaurus A group is a denser environment that is
possibly in a more advanced dynamical stage.
