The Effect of Splashback on Weak Lensing Mass Estimates of Galaxy Clusters and Groups

TL;DR

This paper investigates how the splashback radius influences weak lensing mass estimates of galaxy clusters and groups, revealing potential biases that could affect cosmological parameter measurements.

Contribution

It demonstrates that neglecting the splashback feature can bias mass estimates of galaxy groups, especially around 10^{13.5} solar masses, impacting cosmological inferences.

Findings

Splashback radius significantly affects mass estimates of group-sized halos.

Ignoring splashback can bias mass measurements by over 0.1 dex.

Such biases could lead to underestimating cosmological parameters like Ω_m.

Abstract

The splashback radius of a dark matter halo, which corresponds to the first apocenter radius reached by infalling matter and substructures, has been detected around galaxy clusters using a multitude of observational methods, including weak lensing measurements. In this manuscript, we present how the splashback feature in the halo density profile affects galaxy cluster masses derived through weak lensing measurements if it is not accounted for. We find that the splashback radius has an increasingly large effect on group-sized halos towards $M_{200m} \sim 10^{13.5} \mathrm{M_\odot}$. Depending on the model and the radial scale used, the cluster/group masses can be biased low by more than 0.1 dex. This bias, in turn, would result in a slightly lower $\Omega_m$ value if propagated into a cluster cosmology analysis. The splashback effect with group-sized dark matter halos may become important to consider, given the increasingly stringent cosmological constraints coming from optical wide-field surveys.