Impact of Dark Matter Substructure on the Matter and Weak-Lensing Power Spectra

We explore the effect of substructure in dark matter halos on the power spectrum and bispectrum of matter fluctuations and weak-lensing shear. By experimenting with substructure in a cosmological N = 512^3 simulation, we find that when a larger fraction of the host halo mass is in subhalos, the resulting power spectrum has less power at 1 <~ k <~100 h Mpc^-1 and more power at k >~100 h Mpc^-1. We explain this effect using an analytic halo model including subhalos, which shows that the 1 <~k<~100 h Mpc^-1 regime depends sensitively on the radial distribution of subhalo centers, while the interior structure of subhalos is important at k >~100 h Mpc^-1. The corresponding effect on the weak-lensing power spectrum due to substructures is up to ~11% at angular scale l <~10^4. Predicting the nonlinear power spectrum to a few percent accuracy for future surveys would therefore require large cosmological simulations that also have exquisite numerical resolution to model accurately the survivals of dark matter subhalos in the tidal fields of their hosts.