Quantifying the Impact of Cosmological Parameter Uncertainties on Strong Lensing Models With an Eye Toward the Frontier Fields

TL;DR

This study demonstrates that uncertainties in cosmological parameters significantly affect the accuracy of strong lensing models for galaxy clusters, emphasizing the need to incorporate these uncertainties in future analyses.

Contribution

It is the first comprehensive assessment of how cosmological parameter uncertainties impact strong lensing models of galaxy clusters, highlighting their importance.

Findings

Magnification maps vary significantly with different cosmologies.

Model fitting uncertainties are smaller than cosmological uncertainties.

Mass profile estimates are relatively insensitive to cosmological variations.

Abstract

We test the effects of varying the cosmological parameter values used in the strong lens modeling process for the six Hubble Frontier Fields (HFF) galaxy clusters. The standard procedure for generating high fidelity strong lens models includes careful consideration of uncertainties in the output models that result from varying model parameters within the bounds of available data constraints. It is not, however, common practice to account for the effects of cosmological parameter value uncertainties. The convention is to instead use a single fiducial "concordance cosmology" and generate lens models assuming zero uncertainty in cosmological parameter values. We find that the magnification maps of the individual HFF clusters vary significantly when lens models are computed using different cosmological parameter values taken from recent literature constraints from space- and ground-based experiments. Specifically, the magnification maps have average variances across the best fit models computed using different cosmologies that are comparable in magnitude to - and as much as 2.5 times larger than - the model fitting uncertainties in each best fit model. We also find that estimates of the mass profiles of the cluster cores themselves vary only slightly when different input cosmological parameters are used. We conclude that cosmological parameter uncertainty is a non-negligible source of uncertainty in lens model products for the HFF clusters, and that it is important that current and future work which relies on precision strong lensing models take care to account for this additional source of uncertainty.