1611.02657
Dissecting the evolution of dark matter sub haloes in the Bolshoi simulation
van den Bosch
Present a comprehensive analysis of the evolution of DM sub haloes in the Bolshoi sim. Identify a complete set of 12 unique evolution channels by which sub haloes evolve in between sim outputs, and study their relative importance and demographics. Show that instantaneous masses and maximum circular velocities of individual sub haloes are extremely noisy, despite the use of a sophisticated, phase-space-based halo finder. Also show that sub haloes experience frequent penetrating encounters with other sub haloes (on average about one per dynamical time), and that sub haloes whose epicenter lies outside the virial radius of their host (the 'ejected' or 'backsplash' haloes) experience tidal forces that modify their orbits. This results in an average fractional subhalo exchange rate among host haloes of roughly 0.01 per Gyr (at the present time). In addition, show that there are 3 distinct disruption channels; one in which sub haloes drop below the mass resolution limit of the sim, one in which subhaloes merge with their host halo largely driven by dynamical friction, and one in which sub haloes abruptly disintegrate. Estimate that roughly 80 percent of all subhalo disruption in the Bolshoi sim is numerical, rather than physical. This over-merging is a serous road-block for the use of numerical sims to interpret small scale clustering, or for any other study that is sensitive to the detailed demographics of DM substructure.
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