The Distribution of Satellites in the TNG100 Simulation based on Time Spent in Halo

An important test of the Λ Cold Dark Matter model is the degree to which galaxy dark matter halos follow the predicted, characteristic density profile. In this Note, we explore the use of satellite galaxies as luminous tracers of halo mass density profiles as a function of the time since they joined the halos. We perform this investigation in the TNG100 simulation, where we can obtain precise locations of satellite galaxies and dark matter particles. We find that, by adopting a more accurate definition of joining redshift compared to a previous investigation, the oldest satellites are better, but not perfect tracers of the dark matter distribution.