Tip of the red giant branch distances to the dwarf galaxies dw1335-29
  and dw1340-30 in the Centaurus group
  The abundance and spatial distribution of dwarf galaxies are excellent
empirical benchmarks to test models of structure formation on small scales. The
nearby Centaurus group, with its two subgroups centered on CenA and M83, stands
out as an important alternative to the Local Group for scrutinizing
cosmological model predictions in a group of galaxies context. We have obtained
deep optical images of three recently discovered M83 satellite galaxy
candidates with the FORS2 instrument mounted on the Very Large Telescope. We
aim to confirm their group membership and study their stellar population. Deep
VI-band photometry is used to resolve the brightest stars in our targets.
Artificial star tests are performed to estimate the completeness and
uncertainties of the photometry. The color-magnitude diagrams reveal the red
giant branch (RGB) stars allowing to use the Sobel edge detection method to
measure the magnitude of the RGB tip and thus derive distances and group
membership for our targets. The mean metallicity of the dwarf galaxies are
further determined by fitting BASTI model isochrones to the mean RGB locus. We
confirm the two candidates, dw1335-29 and dw1340-30, to be dwarf satellites of
the M83 subgroup, with estimated distances of 5.03 +- 0.24 Mpc and 5.06 +- 0.24
Mpc, respectively. Their respective mean metallicities of <[Fe/H]> = -1.79 +-
0.4 and <[Fe/H]> = -2.27 +- 0.4 are consistent with the metallicity-luminosity
relation for dwarf galaxies. The third candidate, dw1325-33, could not be
resolved into stars due to insufficiently deep images, implying its distance
must be larger than 5.3 Mpc. Using the two newly derived distances we assess
the spatial distribution of the galaxies in the M83 subgroup and discuss a
potential plane-ofsatellites around M83.
