The Dependence of Subhalo Abundance on Halo Concentration
  Hierarchical structure formation implies that the number of subhalos within a
dark matter halo depends not only on halo mass, but also on the formation
history of the halo. This dependence on the formation history, which is highly
correlated with halo concentration, can account for the super-Poissonian
scatter in subhalo occupation at a fixed halo mass that has been previously
measured in simulations. Here we propose a model to predict the subhalo
abundance function for individual host halos, that incorporates both halo mass
and concentration. We combine results of cosmological simulations with a new
suite of zoom-in simulations of Milky Way-mass halos to calibrate our model. We
show the model can successfully reproduce the mean and the scatter of subhalo
occupation in these simulations. The implications of this correlation between
subhalo abundance and halo concentration are further investigated. We also
discuss cases in which inferences about halo properties can be affected if this
correlation between subhalo abundance and halo concentration is ignored; in
these cases our model would give a more accurate inference. We propose that
with future deep surveys, satellite occupation in the low-mass regime can be
used to verify the existence of halo assembly bias.
