Universal Multistream Radial Structures of Cold Dark Matter Halos

Virialized halos of cold dark matter generically exhibit multi-stream structures accreted within an outermost radial caustic known as the splashback radius. By tracking particle trajectories that accrete onto in cosmological $N$-body simulations, we count their number apocenter passages ($p$), and use them to characterize structure particles. We find density profile for each stream, classified by passages, exhibits universal features, can be described a double power-law function comprising inner shallow outer steep slopes indices $-1$ $-8$, respectively. Surprisingly, these properties hold over wide range halo masses. The double-power law feature is persistent when dividing sample concentration or accretion rate. dependence characteristic scale amplitude on $p$ cannot replicated self-similar solutions, requiring consideration complexities such distribution angular momentum mergers.