The splashback radius of halos from particle dynamics. II. Dependence on mass, accretion rate, redshift, and cosmology

Understand

The splashback radius $R_{\rm sp}$, the apocentric radius of particles on their first orbit after falling into a dark matter halo, has recently been suggested as a physically motivated halo boundary that separates accreting from orbiting material.

• Using the SPARTA code presented in Paper I, we analyze the orbits of billions of particles in cosmological simulations of structure formation and measure $R_{\rm sp}$ for a large sample of halos that span a mass range from dwarf galaxy to massive cluster halos, reach redshift 8, and include WMAP, Planck, and self-similar cosmologies.
• We analyze the dependence of $R_{\rm sp}/R_{\rm 200m}$ and $M_{\rm sp}/M_{\rm 200m}$ on the mass accretion rate $\Gamma$, halo mass, redshift, and cosmology.
• The scatter in these relations varies between 0.02 and 0.1 dex.