Testing the two planes of satellites in the Centaurus Group
  The existence of satellite galaxy planes poses a major challenge for the
standard picture of structure formation with non-baryonic dark matter. Recently
Tully et al. (2015) reported the discovery of two almost parallel planes in the
nearby Cen A group using mostly high-mass galaxies (M$_B$ $<$ -10 mag) in their
analysis. Our team detected a large number of new group member candidates in
the Cen A group (M\"uller et al. 2016). This dwarf galaxy sample combined with
other recent results from the literature enables us to test the galaxy
distribution in the direction of the Cen A group and to determine the
statistical significance of the geometric alignment. Taking advantage of the
fact that the two galaxy planes lie almost edge-on along the line of sight, the
newly found 13 group members by Crnojevic et al. (2014, 2016) and our 16 new
Cen A group candidates (M\"uller et al. 2016) can be assigned relative to the
two planes. We use various statistical methods to test whether the distribution
of galaxies follows a single normal distribution or shows evidence of
bimodality as it has been reported earlier. We confirm that the data used for
the Tully et al. (2015) study support the picture of a bimodal structure.
However, when the new galaxy samples are included, the gap between the two
galaxy planes is closing and the significance level of the bimodality is
reduced. Instead, the plane that contains Cen A becomes more prominent. We
found evidence that the galaxy system around Cen A is made up of only one plane
of satellites. This plane is almost orthogonal to the dust plane of Cen A.
Accurate distances to the new dwarf galaxies will be required to measure the
precise 3D distribution of the galaxies around Cen A.
