The properties of dwarf spheroidal galaxies in the Cen A group: Stellar
  populations, internal dynamics, and a heart-shaped Halpha ring
  Dwarf spheroidal galaxies (dSphs) have been extensively investigated in the
Local Group, but their low luminosity and surface brightness make similar work
in more distant galaxy groups challenging. Modern instrumentation unlocks the
possibility of scrutinizing these faint systems in other environments,
expanding the parameter space of group properties. We use MUSE spectroscopy to
study the properties of 14 known or suspected dSph satellites of Cen A. Twelve
targets are confirmed to be group members based on their radial velocities. Two
targets are background galaxies at 50 Mpc: KK 198 is a face-on spiral galaxy,
and dw1315-45 is an ultra-diffuse galaxy with an effective radius of 2300 pc.
The 12 confirmed dSph members of the Cen A group have old and metal-poor
stellar populations and follow the stellar metallicity-luminosity relation
defined by the dwarf galaxies in the Local Group. In the three brightest dwarf
galaxies (KK 197, KKs 55, and KKs 58), we identify globular clusters, as well
as a planetary nebula in KK 197, although its association with this galaxy
and/or the extended halo of Cen A is uncertain. Using four discrete tracers, we
measure the velocity dispersion and dynamical mass of KK 197. This dSph appears
dark matter dominated and lies on the radial acceleration relation of
star-forming galaxies within the uncertainties. It also is consistent with
predictions stemming from modified Newtonian dynamics (MOND). Surprisingly, in
the dwarf KK 203 we find an extended Halpha ring. Careful examination of Hubble
Space Telescope photometry reveals a very low level of star formation at ages
between 30-300 Myr. The Halpha emission is most likely linked to a 40 Myr old
supernova remnant, although other possibilities for its origin cannot be
entirely ruled out.
