Satellite galaxies in the Illustris-1 simulation: anisotropic locations
  around relatively isolated hosts
  We investigate the locations of satellite galaxies in the z = 0 redshift
slice of the hydrodynamical Illustris-1 simulation. As expected from previous
work, the satellites are distributed anisotropically in the plane of the sky,
with a preference for being located near the major axes of their hosts. Due to
misalignment of mass and light within the hosts, the degree of anisotropy is
considerably less when satellite locations are measured with respect to the
hosts' stellar surface mass density than when they are measured with respect to
the hosts' dark matter surface mass density. When measured with respect to the
hosts' dark matter surface mass density, the mean satellite location depends
strongly on host stellar mass and luminosity, with the satellites of the
faintest, least massive hosts showing the greatest anisotropy. When measured
with respect to the hosts' stellar surface mass density, the mean satellite
location is essentially independent of host stellar mass and luminosity. In
addition, the satellite locations are largely insensitive to the amount of
stellar mass used to define the hosts' stellar surface mass density, as long as
at least 50% to 70% of the hosts' total stellar mass is used. The satellite
locations are dependent upon the stellar masses of the satellites, with the
most massive satellites having the most anisotropic distributions.
