Weak lensing calibration of mass bias in the REFLEX+BCS X-ray galaxy cluster catalogue

TL;DR

This study uses weak gravitational lensing to calibrate and identify biases in X-ray mass estimates of galaxy clusters from the REFLEX and BCS catalogues, revealing significant underestimation affecting cosmological analyses.

Contribution

It provides the first weak lensing calibration of masses for the REFLEX+BCS cluster sample, quantifying the bias in X-ray mass estimates and its impact on cosmological parameters.

Findings

X-ray masses are underestimated by about 25%.

Mass bias can significantly affect cosmological parameter estimates.

Weak lensing provides an independent calibration method.

Abstract

The use of large, X-ray selected galaxy cluster catalogues for cosmological analyses requires a thorough understanding of the X-ray mass estimates. Weak gravitational lensing is an ideal method to shed light on such issues, due to its insensitivity to the cluster dynamical state. We perform a weak lensing calibration of 166 galaxy clusters from the REFLEX and BCS cluster catalogue and compare our results to the X-ray masses based on scaled luminosities from that catalogue. To interpret the weak lensing signal in terms of cluster masses, we compare the lensing signal to simple theoretical Navarro-Frenk-White models and to simulated cluster lensing profiles, including complications such as cluster substructure, projected large-scale structure, and Eddington bias. We find evidence of underestimation in the X-ray masses, as expected, with $\langle M_{\mathrm{X}}/M_{\mathrm{WL}}\rangle = 0.75 \pm 0.07$ stat. $\pm 0.05$ sys. for our best-fit model. The biases in cosmological parameters in a typical cluster abundance measurement that ignores this mass bias will typically exceed the statistical errors.