Metal-poor nuclear star clusters in two dwarf galaxies near Centaurus A
  suggesting formation from the in-spiraling of globular clusters
  Studies of nucleated dwarf galaxies can constrain the scenarios for the
formation and evolution of nuclear star clusters (NSC) in low-mass galaxies and
give us insights on the origin of ultra compact dwarf galaxies (UCDs). We
report the discovery of a NSC in the dwarf galaxy KKs58 and investigate its
properties together with those of another NSC in KK197. Both NSCs are hosted by
dwarf elliptical galaxies of the Centaurus group. Combining ESO VLT MUSE data
with photometry from VLT FORS2, CTIO Blanco DECam, and HST ACS, as well as
high-resolution spectroscopy from VLT UVES, we analyse the photometric,
kinematic and stellar population properties of the NSCs and their host
galaxies. We confirm membership of the NSCs based on their radial velocities
and location close to the galaxy centres. We also confirm the membership of two
globular clusters (GCs) and detect oblate rotation in the main body of KK197.
Based on high signal-to-noise spectra taken with MUSE of the NSCs of both KKs58
and KK197 we measure low metallicities, [Fe/H] = $-1.75 \pm 0.06$ dex and
[Fe/H] = $-1.84 \pm 0.05$ dex, and stellar masses of $7.3 \times 10^5 M_\odot$
and $1.0 \times 10^6 M_\odot$, respectively. Both NSCs are more metal-poor than
their hosts that have metallicities of $-1.35 \pm 0.23$ dex (KKs58) and $-0.84
\pm 0.12$ dex (KK197). This can be interpreted as NSC formation via the
in-spiral of GCs. The masses, sizes and metallicities of the two NSCs place
them among other NSCs, but also among the known UCDs of the Centaurus group.
This indicates that NSCs might constitute the progenitors of a part of the
low-mass UCDs, although their properties are almost indistinguishable from
typical GCs.
