Left panel: the un-evolved subhalo mass distribution as a function of m _a / M ₀ for host halos of different final masses at z = 0. Here model predictions (lines) are compared with the results obtained from both the 300  h ⁻¹ Mpc box (open circles) and 100  h ⁻¹ Mpc box (filled triangles) N-body simulations of the same cosmology. For comparison, we also include in the figure the fitting formula obtained by Giocoli et al. (2008a) as the solid line. Right panel: The predicted un-evolved subhalo mass functions for scale-free models with n = 0, −1, and −2. For comparison, we also include in the figure the model prediction for the ΛCDM model considered in this paper.