Infall caustics in dark matter halos?

Understand

We show that most particle and subhalo orbits in simulated cosmological cold dark matter halos are surprisingly regular and periodic: The phase space structure of the outer halo regions shares some of the properties of the classical self-similar secondary infall model.

• Some of the outer branches are clearly visible in the radial velocity - radius plane at certain epochs.
• However, they are severely broadened in realistic, triaxial halos with non-radial, clumpy, mass accretion.
• This prevents the formation of high density caustics: Even in the best cases there are only broad, very small (<10 percent) enhancements in the spherical density profile.