On galaxy scales, the cold dark matter model makes two clear predictions: the dark matter halos of large, bright galaxies should be mildly triaxial and the overall mass distribution should follow a universal density profile that is often parameterized as a Navarro, Frenk & White profile. To test these predictions, some sort of luminous tracer of the halo potential is necessary. The locations of small, faint satellite galaxies could, potentially, be useful tracers of the gravitational potentials of their host galaxies’ dark matter halos. To be truly useful tracers, however, the spatial distributions of the satellites must closely follow that of the dark matter. Here I will show recent results that indicate the satellites of bright, isolated galaxies in both the observed universe and Lambda CDM show remarkably lopsided distributions. The lopsidedness is driven by the satellites of blue host galaxies, but is also present for the satellites of red host galaxies. In addition, I will show that, when selected in 3D, the spatial distributions of satellite galaxies in Lambda CDM are sensitive to the details of galaxy formation and evolution that are adopted in magnetodynamical simulations and close agreement between the spatial distribution of the satellites and the spatial distribution of the mass surrounding the host galaxies can be largely coincidental in many cases.
