Fig. 2: Comparison of the radial distribution and anisotropy of the classical MW satellites with those of simulated ΛCDM counterparts.
From: The Milky Way’s plane of satellites is consistent with ΛCDM
On the first two panels, the thick black lines show data for the MW satellites and the thin lines show data from the simulations. Sag: Sagittarius; Umi: Ursa Minor; Dra: Draco; Sxt: Sextans; Scl: Sculptor; Car: Carina; For: Fornax. On all panels, lines and symbols for the simulations are coloured by c/a as shown on the right to identify highly anisotropic (red) and more isotropic (blue) systems. The left panel shows the radius, ri, of the ith closest satellite. The centre panel shows the sum of the squares of the radii of the closest i satellites, normalized by the sum of all 11 satellites. The square of the radius determines each satellite’s contribution to the inertia tensor; the Gini coefficient of inertia, G, quantifies the inequality of these contributions and corresponds to the distance of each line from the dotted line. The right panel shows the correlation between the Gini coefficient and anisotropy, c/a, for ‘complete’ sets of satellites (circles), corrected for artificial disruption, coloured by c/a. The solid line shows the estimated median and the dashed lines the 10th and 90th percentiles. The black circle denotes the Milky Way’s present values of G and c/a and the lines around it show its most likely (bold) and Monte Carlo sampled (thin) evolution over the past 0.5 Gyr. The anisotropy correlates with the Gini coefficient. Without accounting for artificial disruption of satellites in ΛCDM simulations (‘incomplete’, faint crosses), the Milky Way’s satellites are much more centrally concentrated and much more anisotropic. However, when this is taken into account, the MW lies within the scatter.
