Classifying the satellite plane membership of Centaurus A’s dwarf galaxies using orbital alignment constraints

The flattened, possibly co-rotating plane of satellite galaxies around Centaurus A, if more than a fortuitous alignment, adds to the pre-existing tension between well-studied Milky Way and M31 planes $\Lambda$CDM model structure formation. It was recently reported that A (CASP) may be rotationally supported, but further understanding system's kinematics is elusive in absence full three-dimensional velocities. We constrain transverse velocities 27 satellites would stabilise plane, classify by whether their possible orbits are consistent with CASP. Five identified unlikely participate two which clearly non-members. Despite previously line-of-sight velocity trend suggestive common motion, 17 out 22 potential CASP members either orbital direction within both range as well when limiting those plane. On other hand, disregarding 5 off-plane found inconsistent membership enhances significance CASP's fivefold. Our results robust different mass estimates halo, adoption spherical or triaxial NFW potentials.