The Density Profile of Dynamical Halos

TL;DR

This paper investigates the density profiles of dynamical dark matter halos, revealing that their orbiting particle distribution depends primarily on halo radius, with scatter influenced by formation time, enhancing understanding of halo structure.

Contribution

It introduces a characterization of the orbiting profile dependence on halo radius and quantifies the scatter and its relation to formation time.

Findings

Scatter in halo radius at fixed mass is about 16%.

Late-forming halos are more compact.

Accounting for formation time reduces scatter to 11%.

Abstract

Among the most fundamental properties of a dark matter halo is its density profile. Motivated by the recent proposal by Garc\'ia et al. [R. Garc\'ia et. al., MNRAS 521, 2464 (2023)] to define a dynamical halo as the collection of orbiting particles in a gravitationally bound structure, we characterize the mean and scatter of the orbiting profile of dynamical halos as a function of their orbiting mass. We demonstrate that the orbiting profile of individual halos at fixed mass depends on a single dynamical variable -- the halo radius $r_{\rm h}$ -- which characterizes the spatial extent of the profile. The scatter in halo radius at fixed orbiting mass is $\approx 16\%$. Only a small fraction of this scatter arises due to differences in halo formation time, with late-forming halos being more compact (smaller halo radii). Accounting for this additional correlation results in an $\approx 11\%$ scatter in halo radius at fixed mass and halo formation time.