MUSE observations of dwarf galaxies and a stellar stream in the M 83 group

Spectroscopy for faint dwarf galaxies outside of our own Local Group is challenging. Here, we present MUSE spectroscopy to study the properties of four known dwarf satellites and one stellar stream (KK 208) surrounding the nearby grand spiral M 83, which resides together with the lenticular galaxy Cen A in the Centaurus group. This data completes the phase-space information for all known dwarf galaxies around M 83 down to a completeness of -10 mag in the V band. All studied objects have an intermediate to old and metal-poor stellar population and follow the stellar luminosity-metallicity relation defined by the Local Group dwarfs. For the stellar stream, we serendipitously identify a previously unknown globular cluster that is old and metal-poor. Two dwarf galaxies (NGC 5264 and dw1341-29) may be a bound satellite of a satellite system due to their proximity and shared velocities. With our access to the positions and velocities of 13 dwarfs around M 83, we estimated the mass of the group with different estimators. Ranging between 1.3 and 3.0×10¹² M_⊕ for the halo mass, we find it to be larger than previously assumed. This may impact the previously reported tension for cold dark matter cosmology with the count of dwarf galaxies. In contrast to Cen A, we do not find a corotating plane of satellites around M 83.