How Accurately Can We Detect the Splashback Radius of Dark Matter Halos and its Correlation With Accretion Rate?

TL;DR

This study evaluates the accuracy of different methods in detecting the splashback radius of dark matter halos using simulations, and explores its correlation with accretion rates, highlighting potential biases and future observational prospects.

Contribution

It systematically compares various measurement techniques for the splashback radius and assesses their precision and biases using simulations, linking it to accretion rates.

Findings

Density and subhalo profiles estimate different percentiles of the splashback radius.

A second caustic at low accretion rates can bias measurements.

Upcoming surveys may constrain the splashback-accretion rate relation.

Abstract

The splashback radius ($R_{\rm sp}$) of dark matter halos has recently been detected using weak gravitational lensing and cross-correlations with galaxies. However, different methods have been used to measure $R_{\rm sp}$ and to assess the significance of its detection. In this paper, we use simulations to study the precision and accuracy to which we can detect the splashback radius with 3D density, 3D subhalo, and weak lensing profiles. We study how well various methods and tracers recover $R_{\rm sp}$ by comparing it with the value measured directly from particle dynamics. We show that estimates of $R_{\rm sp}$ from density and subhalo profiles correspond to different percentiles of the underlying $R_{\rm sp}$ distribution of particle orbits. At low accretion rates, a second caustic appears and can bias results. Finally, we show that upcoming lensing surveys may be able to constrain the splashback-accretion rate relation directly.